جستجوی مقالات مرتبط با کلیدواژه « داده های تابلویی » در نشریات گروه « کشاورزی »

Environmental pollution is one of the most important problems that most developing countries face today, which in addition to environmental problems has negative economic and social consequences. Studies show that the shadow economy and institutional factors can be influential factors on the quality of the environment in developing countries, and few studies have been conducted on the effect of these factors on environmental pollution at the same time. The shadow economy occupies a large part of the economy of developing countries, which can affect the quality of the environment, and institutional factors can affect the quality of the environment through different channels, such as controlling and influencing the shadow sector. Therefore, the current research has been conducted with the aim of investigating the effective factors of environmental pollution in oil developing countries. Using the panel data model and the generalized least squares method for the period of 2009-2020, the results have shown that the shadow economy and the rule of law directly increase pollution and the interaction effect of the rule of law and the shadow economy has led to a reduction in pollution; Therefore, it can be expected that by controlling the shadow sector, increasing the rule of law will lead to a reduction in pollution. Also, the results have shown that corruption control has directly reduced pollution and the interaction effect of rule of law and corruption control has led to a reduction in pollution. Therefore, controlling corruption and increasing the rule of law at the same time plays an important role in reducing pollution in oil countries. Also, the results confirm the hypothesis of Kuznets for the group of oil developing countries at the beginning of the development path.

The aim of this study was to evaluate the possible changes of yield and related welfare of two major groups of cereals and vegetable crops as a result of two climatic variables (rainfall and temperature) variations in Khuzestan province. For estimation of crop response production function of selected study crops, meteorological data including rainfall, minimum temperature, maximum temperature and relative humidity of 13 stations across the province for the years 1991 to 2019 were collected. Crop response production functions for different climate zones of the province were determined and possible effects of climatic variation on producer / consumer welfare were assessed. According to the results, the welfare of the cereal crops, the producer welfare surplus is higher than the consumer welfare surplus. A decreasing trend in welfare was observed under climate change scenarios. Also, the obtained results of projected welfare of the vegetables crops showed that the consumer welfare surplus is higher than the producer welfare surplus. In general, the welfare surplus of cereals is higher than that of summer vegetable crops and hence as a adaption strategy, cereal cultivation may be recommended.

Extended Abstract

Introduction and

The agricultural sector is one of the most important economic sectors in every country, which in Iran has significant advantages such as land diversity, cheap labor, and less need for complex technology to produce all kinds of products in different seasons of the year. Therefore, it,s maded strengthening is essential for economic development, employment, and increasing non-oil exports. This article investigates the factors affecting the trade of agricultural products between Iran and the Russian Federation using the gravity model.

First, necessary statistics and information were collected from the websites of the Central Bank and the World Bank for the period from 2010 to 2020. Then, in order to investigate the influencing factors on the volume of bilateral trade of agricultural products of Iran and Russia, the generalized gravity model was used. Before estimating the model, first the reliability of the variables was checked through the Levin-Lin and Chu test, and then the gravity model was estimated using the panel data method. In this study, the data were used separately for the export sector, once for import and finally for the whole trade (exports + imports) to determine the effects of different variables on each sector. Then, the Hausman test results were analyzed to select the most suitable part for analyzing the results.

The results of Levin-Lin and Chow tests showed that all variables were significant and panel data were static. The estimated results of the gravity model for the three sections under study are statistically significant based on F-statistics. Therefore, the null hypothesis is rejected, indicating that the intercepts are different from different time periods and panel data should be used. The results of the Hausman test for exports, imports, and trade were calculated as 0.214, 0.4359, and 0.000 respectively, based on which trade estimation was selected for analyzing the results. Estimating the gravity model for trade indicated that the coefficient of the variable Gross Domestic Product (GDP) of both countries, which represents their economic size, is an important factor in the bilateral trade volume of agricultural products between Iran and Russia. Also, distance, real exchange rate, and virtual variable of membership in the Eurasian Economic Union are the effective factors in the bilateral trade volume of agricultural products between Iran and Russia.

Generally, increasing the Gross Domestic Product (GDP) of both countries leads to an increase in bilateral trade of agricultural products between Iran and the Russian Federation. Therefore, it is suggested that measures be taken in the decision-making of policy makers in the field of membership in organizations and commercial agreements, especially in the field of agriculture.

The agriculture section as a subsection of our economy receives the most impact under the climate fluctuations. Climate change is an unsustainable factor affecting the yield of agricultural crops. Therefore, agricultural production, especially rainfed cultivation, has a high correlation with climatic factors. Climate change, in addition to affecting the production of agricultural crops, affects the sustainability and performance of agricultural products by influencing water resources. Agricultural product performance forecasting is one of the management tools in agricultural sector planning and policy making. The purpose of the current study was to evaluate the yield and production rate of three summer crops including cucumber, tomato and watermelon due to climate change in Khuzestan province and their prediction for the years 2025 to 2100.

In order to evaluate the reaction function of summer crops yield in Khuzestan province, meteorological data including precipitation, minimum temperature, maximum temperature and relative humidity of 13 meteorological stations including Ahvaz, Izeh, Andimeshk, Mahshahr, Behbahan, Dezful, Azadegan, Ramhormoz, Shushtar, Masjed Soleiman, Omidieh, Shadegan and Shoush was collected during the years 1991 to 2020. Excel and SPSS software were used to calculate and analyze the indicators. The climatic indices of Khuzestan province were divided into two climatic regions. Region (1) included Ahvaz, Mahshahr, Behbahan, Shoushtar, Omidie, Shadegan and Shoush, and region (2) included Dezful, Azadegan, Ramhormoz, Masjed Soliman and Andimeshk. The yield function of three products including cucumber, tomato and watermelon at two regions was estimated using panel data and Eviews software. Then, the yield and production rate of crops were predicted using the climate forecasting scenarios for the years 2025 to 2100.

The results showed that temperature had a negative and significant effect on the yield of tomato in region (1) and region (3), but it had a positive and significant effect on the yield of region (2). Rainfall had a negative and significant effect on the yield of tomato in region (1). But rainfall had a positive and significant effect on the yield of crops in region (2) and (3). Humidity had a positive and significant effect on tomato in region (1) and (2), but it had a negative effect on region (3). Temperature had a positive and significant effect on cucumber yield in region (1) and region (3). But it had a negative effect on the yield of cucumber in region (2). Rainfall had a positive and significant effect on cucumber yield in region (1) and (3). But it had a negative effect on the performance of region (2). Humidity also had a positive effect on the performance of cucumber in region (1), but it had a negative effect on the performance of region (2) and (3). Temperature had a negative and significant effect on watermelon yield in region (1) and (3), but it had a positive effect on watermelon yield in region (2). Rainfall had a negative and significant effect on the yield of watermelon in region (1), but it did not have a significant effect on the yield of region (2) and (3). Humidity had a negative and significant effect on the yield of watermelon in region (1) and (3), but it had a positive and significant effect on the yield of region (2). Also, the results showed that the highest percentage of yield changes in climate scenarios were related to cucumber in region (3) and watermelon and tomato in region (2). The results of forecasting the production rate of selected crops during the years 2100-2025 showed that the highest production rate was related to tomato in region (2), watermelon in region (2) and watermelon in region (1). Based on the results, during the years 2100-2025, the cultivated area of tomato crop in region (1) showed a more downward trend, but the cultivated area of cucumber crop in region (1) showed a more upward trend.

The results of yield forecasting until year 2100 showed that cucumber crop in region (3) and watermelon and tomato crops in region (2) have respectively higher increase rate of yield. Also, results demonstrated that in region (2), tomato and watermelon have higher production rate, respectively. Given to adverse effects of climate change on the production of studied crops and in order to prevent considerable reduction of production rate, solutions should be provided to adapt more to climate conditions, such as changing the cultivation pattern, optimal management of resources and production of varieties resistant to climate change. Therefore, according to the obtained results, it could be stated that region (2) has a relative advantage in the production of watermelon and tomato crops.

Carbon dioxide emission is one of important challenges facing humanity, which has attracted the attention of many researchers and policymakers in recent years. The purpose of this study is investigating the factors influencing carbon dioxide emission. For achieving the purpose of paper spatial econometrics model and panel data of MENA countries are used over the period of 2000-2015. The results indicate that carbon dioxide emission in the MENA region countries have significant effect on surrounding countries. Also, the variables of energy consumption (0.01), economic globalization (0.134), industrialization (0.405) and urbanization (0.042) have positive and significant effect on carbon dioxide emission in the MENA region. The interaction among energy consumption and globalization (0.361), energy consumption and, industrialization (0.234) and urbanization (0.085) have a positive and significant effect on carbon dioxide emission. According to the results of this study, it is necessary that policymakers should not only focus on the national economic benefits but also consider the national and regional environmental benefits in policy making.

Poverty reduction is one of the important goals of development programs. This study was conducted to investigate the factors affecting rural poverty in provinces of Iran during the years 2011-2018. Poverty Gap Index has been calculated as dependent variable. The log- log regression model of influencing factors on poverty was estimated using the cross section weighted least squares method. Results showed that rural poverty has been an unbalanced long- run phenomenon that has grown over time and covered more people. The coefficients of estimated model showed that the share of province in GDP, areas under cultivation, number of rural comprehensive health service centers and dummy variable of less poor provinces have had significant negative effect on poverty. The value added of agriculture sector, rural consumer price index, family size, trend, first lag of dependent variable and dummy variable of poorer provinces have had significant positive effect on poverty gap index. The negative effect of the share of province in GDP and areas under cultivation on poverty confirmed the important role of production infrastructures and economic opportunities in poverty reduction. Significant positive effect of the value added of agriculture sector can be an evidence of small contribution of villagers in value added of this sector. Based on the results of this study, it is suggested to avoid the concentration of investment, resources and production opportunities in richer provinces and to pay attention to balanced regional development to reduce poverty in poor provinces. Also anti-inflationary policies will reduce poverty in all regions. Since poverty has been a long-run and growing phenomenon in most regions, long- run planning in production and welfare infrastructures is needed to eradicate poverty.

This paper aimed to examine the effects of ICT developments on the renewable energy consumption in the economic sectors of Iran. The panel data for study were obtained from three sectors of agriculture, industry, and services within the 2000-2016 timeframe; the unit-root test showed that the variables were both stationary and nonstationary. As a result, the mean group was used to estimate the long-run effects, and it revealed that, in the long run, the increase in the number of the Internet and cellphone users decreases the renewable energy consumption. In addition, the GDP and investment growth increases the energy consumption, because the growth of information and communication technology infrastructures develops the e-government and teleworking and reduces the traffic, and, in turn, conserves the energy. However, the increase in the number of landline and cellphone users in the short run increases the energy consumption. The GDP increase will also raise the energy consumption in the short run.

Optimal use of energy inputs and increasing productivity of energy lead to less production costs, less greenhouse gas emission also, less negative effects of agricultural inputs on the environment. This study aims to examine the energy balance of sugar beet production in Iran and compares the economic and environmental dimensions of expanding sugar beet production. For this purpose, production function of sugar beet was estimated using Panel data of five provinces of Hamedan, Kermanshah, Khorasan Razavi, Fars and West Azerbaijan for 2000-2015 period. Results showed that the highest energy inputs are chemical fertilizer, machinery and labor, respectively. Also, with a net energy gain of about 643 GJ, 23.53 energy ratio and 1.4 MJ/Kg energy productivity, an increase in sugar beet production is desirable in viewpoint of energy balance. The estimated Cobb- Douglas production function showed that only machinery and farmyard manure were used in the economic range. The MPPs of two inputs of machinery and farmyard manure were higher than other inputs. Also, an increase in sugar beet yield using these two inputs causes less CO2 emission. The significant coefficient of Dummy variable showed that the yield of sugar beet in Fars and Khorasan provinces is significantly lower than other provinces. The sum of the significant coefficients of the energy inputs indicated a decreasing returns to scale. Based on the results of this study, expanding mechanized cultivation and optimal use of monogram seeds, also, reducing subsidies and realizing the price of chemical fertilizers to reduce the use of this input are suggested.

The agriculture section as a subsection of our economy receives the most impact under the climate fluctuations. Climate change is an unsustainable factor affecting the yield of agricultural crops. Therefore, recognition of climate parameters and their effect on crops is one of the most important factors in increasing yield. Vegetable production globally, as a wage-earning profession, is very effective in improving the general public's economy. The inadequate use of potential climatic facilities causes the destruction of natural resources and the wasting of the national capital. The purpose of this study was to evaluate the yield and production of onion and tomato products due to climate change and its prediction for 2025-2100 in Hormozgan province.

In order to more accurately estimate the function of the reaction of the yield of horticultural products to the climatic components, the climatic indices of Hormozgan province were divided into two climatic regions. Region (1) includes Minab, Hajiabad, Rudan and region (2) includes Bandarlenghe, Band-Abbas, Qeshm and Jask. The yield function of two products, onion and tomato, in the two regions under study was estimated using panel data and Eviews software. Then, using the weather forecasting scenarios, the yield and production of vegetables (onion and tomato) for the years 2025 to 2100 were predicted. Agricultural and climatic data were collected during the years 2003- 2017.

Results showed that the temperature has an opposite effect and rainfall and humidity has a direct effect on the yield of onion and tomato. The most important factor affecting onion production in both regions is the temperature. On the tomato production, the humidity factor in the region (1) and the factor of temperature and humidity in the region (2) are almost the same in terms of effect level. The difference is that the temperature has a negative effect and the humidity has a positive effect on the performance. The negative effect of temperature on the onion yield was higher than that of tomato. The negative effect of temperature on onion production in the region (2) has a higher intensity than the region (1). Performance prediction up to 2100 showed that yield of onion reduce more than yield of tomato. the yield reduction in the region (2) is higher than the region (1). In contrast, the tomato production in the region (1) is higher than the region (2). According to the decline in the yield of two products, the production cuts for both products has been predicted in both regions until the year 2100.

According to the negative effects of climate change on the products under study, we should provide solutions to avoid the harmful effects and to adapt to the climatic conditions. This includes changing the region's cultivation pattern, managing optimal resources and producing climate change resistant seeds. Therefore, it can be stated that the region (1) has a comparative advantage in the production of onion and the region (2) in the production of tomato.

Providing people's feed requirement, raw materials for industry, employment and creating incomes is important; strengthening and developing the agricultural sector has a significant role in consolidating the economic foundations of developing countries; for this reason, the stability and sustainability of agricultural sector growth. For this reason, the stability and sustainability of the agricultural sector are among the main drivers of social stability and economic growth. The purpose of this study is to examine the relationship between the share of agricultural employment with the fear of entrepreneurship in the three categories of high economic growth, sustained economic growth, and unsustainable economic growth. Therefore, the panel data related to fears of failure rates and agricultural employment share in the years of 2008- 2017 for 15 countries and the Panel least squares method were used. The results show that there is an inverse relationship between the share of agricultural employment and the fear of entrepreneurial failure. Investigating the relationship between these three groups showed that there was no significant difference between them. To better understand the environmental factors governing the relationship between industrialization and entrepreneurship, re-sampling should be done. Based on the results, it is suggested that in the conditions of rapid structural changes and in countries with high agricultural share, more government guarantees are needed.

One of the most important issues in the world literature is to measure and assess the degree of competitiveness and monopoly in the markets and determine the structure of the international market. One of the main goals of countries in the world of trade has long been gaining a greater share of the international market. Iran is one of the largest pomegranate producers and exporters in the world. The present study evaluates Iran's pomegranate demand by using parametric models and panel data for countries exporting pomegranates from Iran during the period of 1993 to 2013. The results showed that the price elasticity of the pomegranate demand is -0.06. This means that as prices rise, there is no significant reduction in the demand of the importing countries, and it shows demand of Iran pomegranate in the global market is inelastic. These results are consistent with the calculation indices of the Herfindahl – Hirschman, share of two largest firms and eight largest firms in the pomegranate world market structure, which highlights the strong focus of the market for Iran and India. It seems that that the continuation of the current process may endanger Iran's market power and position. Finding new business models, marketing and participating in international exhibitions are some of the strategies to maintain and expand Iran's pomegranate demand in global markets.

Climate change and its diversity is one of the greatest challenges which will face humanity in this and future centuries and the economic effects of climate change on agriculture have been a concern for policymakers. The effect of climate change on the agricultural sector has been largely harmful: For example, the effects of periodic droughts and floods have always threatened the life of rural populations that depend on agriculture (Ranganathan et al., 2010). According to FAO (2014), an important part of the maize supply in Iran is provided through importation and one of the main reasons for the increase in maize imports over recent years is a decrease in its yield that depends on climatic conditions. Through improvement of domestic production essential steps can be taken towards self-sufficiency in production of this product (Kazemnejad and Gilanpour, 2014). Given that maize is one of the basic agricultural products and considering its importance and strategic role, a survey of the factors affecting production of this product and, in particular, the effect of climatic factors is necessary. So, in this paper the alignment of regional management of maize production and climate change was studied using a spatial model and panel data for 15 provinces during the period 1984-2010.
Material and In this research, a spatial econometric approach was used to study the effect of climatic factors on maize production and, due to the type of available data, a panel data approach has been used. Panel data provides a suitable environment for the development of estimation methods and researchers were able to use cross sectional and time series data to discuss issues that it is not possible to study through time series or cross section data alone (Baltagi, 2005). Climatic variables used in this study included the planting temperature, growth temperature, harvest temperature, planting precipitation and growth precipitation of product.
Results of the Moran test for presence of spatial effects in the panel data showed that there is spatial autocorrelation in the data and the spatial autocorrelation coefficient between the provinces is 0.47. This shows that, in order to survey effect of climatic factors on maize production, we need to consider the geographical situation and vicinity in the model. Estimation of the random effect spatial model (derived from a modified Hausman test) in surveying the impact of climate change on maize production showed that the increase in planting temperature has a negative effect on maize production while the square of planting temperature has positive effect on maize production. Also, harvest temperature has a positive effect on maize production and the square of harvest temperature has negative effect on maize production. Planting precipitation has negative effect and growth temperature has positive effect on maize production; also, the effect of the area under cultivation is positive.
According to the findings, it is advisable to avoid delaying maize planting in warm places such as Khozestan, Isfahan, Ilam, Yazd, Hormozgan and Semnan or, if it is possible, to use heat resistant maize seeds. In areas where the maize harvest is grown in winter, accelerating the harvest under warmer conditions leads to an increase in production. Moreover, it is better to plant maize in Kurdistan and Ghazvin provinces with little delay which is not affected by extreme rainfall of early spring. In Kurdistan, Lorestan and Ilam provinces that have high growth precipitation, it's better for farmers to be insured against systemic risk.

Agricultural commodity export is a main attribute of developing countries and it is the basic force of development, however, developing countries have faced domestic and international instability in their markets and monetary and fiscal policies and these instabilities create a difficult condition for most of producers and exporters. Volatility in exchange market is one of the most important factor and vital concentrate for international trade especially agricultural commodity export. Because of this concern many studies have been conducted in this filed; (Aristotelous, 2001; Chen, 2009 and Sabuhoi and Piri, 2009) .Many of these studies has stated that exchange rate fluctuation has a negative impact on aggregated agricultural export; however, none of them has been focused on the effects of exchange rate fluctuation on exported value of important commodities in long run and short run. In recent years, exchange rate fluctuation has been raised about 6 percent since 2007 to 2010 and it seemed that this phenomenon has a negative impact on agricultural commodity export in Iran. To test this hypothesis exported value of three important commodity (date, orange and grape) and exchange rate volatility since 1970 to 2013 have been used.
Material and

In order to examine the relation between real exchange rate volatility and export values of date, orange and grapes, first GARCH method has been used to draw out exchange rate volatility; then, Panel unite root test has been used to check the level of integration. Since real exchange rate is not heterogeneous for different cross sections Levi-Lin and Chow unit root test has been used for this variable and IPS test has been applied to export value. Pederoni co-integration test has been used to check the integration between these variables. Finally, FMOLS (Fully Modified Ordinary Least Square) and DOLS (Dynamic Ordinary Least Square) methods have been used to estimate long run and short run coefficients.

Main results showed that real exchange rate volatility and export value of selected commodities are Co-integrated. The coefficient estimation of FMOLS and DOLS methods are equal and statically significant; so, these methods aren’t statically different and they showed that real exchange rate volatility has a negative impact on exported value for whole panel. However, the specific coefficient for each commodity showed contradictory behavior in short run and long run; for example real exchange rate fluctuation has a negative and significant impact on all the commodities; but, in short run this variable has a positive and significant impact on exported value. Moreover, based on estimated results it seems that fluctuation in exchange market has a greater impact on more valuable commodities like date.

Considering the importance of agricultural product trade and in order to overcome mono-product economy, this study investigated long term and short term relation between export of grape, orange, date and exchange rate volatilities. To this aim, first the index of exchange volatility using generated autoregressive conditional heteroscedasticity (GARCH) was calculated. In order to investigate the relation between exchange rate volatilities and export value of agricultural product, unit root test and cointegration test related to panel data were used during years 1971-2013. The results of model estimation showed that exchange rate volatilities in short term and long term have respectively positive and negative effects on the export value of orange, grape and date. In long term, the negative effects of Exchange rate volatilities on high-export-value products are more than its effects on low-export-value products. Based on the estimation results we can conclude that, in short run, exporters are willing to increase their interchange and gain profits of the volatility in exchange market; however, in long run exchange rate fluctuation has effect on their long run profit because of instability in price and production, especially for more valuable products. Moreover, these risks can be more harmful in long run because of its impact on investment and production and due to lack of production, most of Iranian exporters will lose their international markets, hence, their volume and values of agricultural commodities export will reduce gradually. Based on the results, Iranian government should create a stable economic condition in long run, present proper information about exchange market future trend and its fluctuation in long run and short run and create a better marketing condition in short run.

Exchange rate volatility is ambiguous and the one of the factors that effecting agricultural trade. Regarding to importance of free trade and economic monoculture crops, the purpose of this study was to investigate the effect of exchange rate uncertainty on the foreign trade of agricultural products for this purpose four crops (pistachio, dates, raisins and walnuts) were selected and required information were gathered for period 1980-2010. For this purpose, first for calculating the uncertainty of exchange rates, generalized auto regressive conditional dissonance variance model (GARCH) were used and then to estimate the relationship between exchange rate and export of agricultural products were used gravity model and panel data method. The results of study showed that the exchange rate uncertainty has a negative effect on the export of agricultural products and pistachios are affected by this uncertainty more than other products. Therefore, creating certainty in the currency markets can be developed important agricultural export products. Also, other results showed that income importing countries has a significant and positive impact on export volumes that should be noted the selection of target markets.

Developing countries, including Iran, have a high degree of volatility of macroeconomic variables. Fluctuations inex change rate, bank interest rate and inflation rate can create insecure environment for in vestorsin Iran. Hence, this study examined the impact of macroeconomic variables on the Tobin’s Q index for the Sugar companies of Tehran Stock Exchange (TSE) during the period between1380-1390. A panel data model in the form of random-effects analysis was performed. The results indicate that the exchange rate, inflation rate and therate of return onassetshavean insignificant negative impact on the Tobin’s Q index. Bank interest rateshave a significant negative impact, while Market value has a significant positive impact on the Tobin’s Q index.

For many years، Iran has traditionally been the largest pistachio producer and exporter in the world. In addition، pistachio is considered as one of the important sources of foreign exchange earnings and it has important role in reducing dependence of the public budget on oil revenues. Given the importance of pistachio in the Iran''s agricultural economy، it is essential to identify the factors that aaffects pistachio exports. The main purpose of present paper is to estimate the export demand function for Iranian pistachio. Using a panel of seven destination markets (including Australia، France، Germany، Japan، Malaysia، Mexico and Switzerland) over the period 1992–2012 and controlling for the endogeneity of the explanatory variables، error component two stage least squares method is used to estimate export demand function. According to the results، all estimated coefficients are significantly different from zero at the five percent level and have the theoretically expected signs. The results show that long-run elasticity of demand for Iran''s pistachio exports with respect to relative prices and real exchange rate changes are considerably greater (in absolute terms) than their corresponding short-run elasticity. The results also suggest that the demand for Iran''s pistachio exports is inelastic with respect to real foreign income in both short- and long-run. Thus، with respect to demand conditions in destination markets، it is necessary to reduce marginal cost of Iranian pistachio producers by elaboration and implementation supportive policies.

Climate change phenomenon is an important environmental challenge of the world that increasing extension of greenhouse gases and remote relationship phenomena accelerate the speed climate change. Decreasing in precipitation level and increasing in air temperature are the recognized consequences of this phenomenon that on yield of agricultural product affects very much. According to the importance of the issue, in the present study climate effects of temperature and precipitation change and amount consumption of agricultural inputs (seed, fertilizer, pesticides and machines) on yield of irrigated wheat strategic product in Shahrood watershed during the years of 2001- 2013 are evaluated. Basic raw data for this study from Meteorological Organization and Agricultural Jihad of Qazvin province were collected. After reviewing static, data in the form a panel with fixed effects was estimated. The result showed that an increase in temperature during the growing season has a negative effect on yield of irrigation wheat, so that the amounts of yield per degree of temperature increase by as much as reduced to 0.683 percent. Also, the result showed that there is a significant relationship between yield of irrigation wheat and amount consumption of product inputs.

Urbanization، population growth and moving from traditional manufacturing industry to accelerate the process of economic development and parallel، significant environmental impacts are left. The purpose of this study is to investigate the effect of different variables such as trade openness، comparative advantage، production levels and other important variables affecting the emission of carbon dioxide gas in various countries of the world. Stata11 software was used to estimate the panel data model of 77 countries over the years 2010-1980. The results indicate that propagation environment، and in particular CO2، in all four groups of countries are associated with prior emission، with a per capita income direct link but with the square of it correlates inversely and have direct link with the ratio of capital to labor and with the square of it correlates inversely and trade openness in high-income countries and moderate negative effect in low-income and middle-income countries is directly related to the bottom.

This paper investigates the effects of advertising، profitability، degree of concentration on the market and Research & Development costs on the Market Share in the Iranian large food and beverage industries during the period of 2000-2011. For this purpose، the study used the statistics associated with large firms-with more than 50 employees. The panel data technique was used to estimate the model. The main results of this paper reveal that، the elasticity for market share with respect to profitability is greater than thoes for other explanatory variables such as advertising cost and R&D cost. Moreover the results indicate that concentration on the market has a positive and significant effect on the Market Share within the large industries. Thus،the main policy recommendations of this study is that Firms and business managers and executives as well as economic authorities can contribute to improve market share through providing the essential conditions to increase the research and development costs، advertising costs، and increase in profitability in the Iranian large beverage industries.