Abstract:  Agricultural science and technology progress is an important driving force for the continuous growth of grain production. Under the conditions of market economy, technological progress in grain production is the result of the combination of relative price changes and resource endowments. The theory of induced innovation believes that the relative change of factor price will lead to technological innovation that saves high-price factors. New technological innovations affect the welfare of different subjects by changing the income distribution pattern of factors relative to marginal output. Therefore, breaking through traditional economics of neutral technical progress assumptions, this study explores mechanism of technical biased progress------elements relative price changes----benefits change, to provide theoretical and empirical basis for improving the efficiency of resource factor allocation and promoting agricultural science and technology policy innovation. The data employed including grain output, grain price and factor price from 2000 to 2016. Biased technology progress welfare effects model is applied to evaluate the production and distribution effect.
The results of welfare effects on grain production technology biased progress show that grain production technology biased progress is helpful for the improvement of the overall social welfare. The producer surplus increased from 4.078 billion Yuan in 2000 to 18.994 billion Yuan in 2016. The consumer surplus increased from 61.799 billion Yuan in 2000 to 205.331 billion Yuan in 2016. The biased evolution of technological progress has led consumers to obtain most of the economic surplus, while the share of producer welfare distribution is small, ranging from 4.4% to 8.5% during the sample period. It is noted that the biased evolution of grain production technology has delayed the emergence of the “agricultural treadmill effect”, that is, in the process of pursuing profit maximization or minimizing costs, grain producers react to the prices of different supply elastic resources and replace expensive production factors with cheap production factors, thus facilitating farmers who adopt biased technology to obtain producer surplus. However, this improvement over time shows a trend of gradual decline after the inflection point, it is increased from 658.77 billion Yuan in 2000 to 2243.25 billion Yuan in 2016, the economic surplus between producers and consumers and the different factors of production are distributed in an unbalanced way, consumers and producer using biochemical technique benefit from the welfare gain, while the producers using mechanical technology is subject to welfare losses.
Secondly, the influence of biased technological progress on factor productivity is heterogeneous. The evolution of China’s grain production technology is mainly based on the chain of comparison of cost and benefit---expanding the use of abundant elements---profit increase---biochemical technology progress, because the growth rate of biochemical technology factor productivity is higher than that of mechanical technology, makes abundant elements in a favorable position in social welfare distribution, leading to the imbalance of technological progress and factor welfare distribution, while factor input relies on the marginal productivity of factors to get compensation and the path dependence of technologically biased evolution will exacerbate this inequality. Therefore, how to adjust the distribution of welfare among different factors of production as well as producers and consumers, to increase the input of factor-based input of mechanical technology, and to induce technological changes in policy or institutional adjustment are important to play a role.
Thirdly, the welfare distribution effect of grain production technology advancement has a phased characteristic. The change in the structure of factor welfare distribution is the result of the combination of the economic development stage and the relative abundance of factor endowments. The influence of biased technological evolution on the welfare distribution of different subjects is affected by the combination of abundant elements and scarce elements. The abolishment of induced institutional change such as agricultural taxes has led to a shift in technological progress from biochemical to mechanical, and increased the income share of scarce factors. Therefore, the biased evolution of food production technology has a significant impact on the distribution of social welfare. The induced technological change provides a possibility for producers to overcome the “agricultural treadmill effect” to obtain the technological benefits of welfare, which is conducive to the promotion of welfare under different conditions and different subjects.
The biased evolution of technological progress has significant differences in the yield and distribution effects of different grain varieties. Rice, corn and wheat show different types of technological advancement bias due to their different resource endowments. The complementarity or replacement of biochemical and mechanical technologies has an important impact on the improvement of overall social welfare. The distribution of factors in the evolution of food production technology has a polarizing effect, which leads to an expansion of the welfare share of biased factors, and the share of non-biased technologies welfare is squeezed. Therefore, the direction of technological progress is matched with the structure of factor distribution, that is, biochemical technology and mechanical technology complement with each other, and the type of technological progress based on natural endowment conditions is more conducive to the increase of overall social welfare. Therefore, advancement in grain production technology needs to choose the direction of technological progress that matches their own factor endowments and through rational distribution of production factors, thus contributing to the improvement of overall social welfare.
In general, the welfare effect of the biased grain production technology advancement is different due to changes in grain varieties and production stages. China’s grain production technology advancement is more biased towards biochemical technology, which is conducive to the improvement of producer welfare using pesticides, fertilizers, and improved production factors. Different food crops have different welfare effects due to different capital-labor substitution elasticity and different demand for mechanization. Therefore, increasing patent protection and implementing technological progress in accordance with changes in factor abundance will help to improve overall social welfare. Moreover, as the economic development reaches a certain level, it needs to change from factor scale expansion to product quality improvement. The combination of technology and capital is more urgent to increase the demand for mechanical technology investment, and the price effects will be improved by increasing the productivity of scarce factors, thus to improve the overall level of social welfare. With the improvement of economic development level and quality, the coupling of biochemistry and mechanical technology will be a new trend of technological change. That is, technological progress is characterized by the dual biased characteristics of capital and labor complementation, which will be more conducive to the maximization of social welfare.

Key words:  grain production technology progress, bias, welfare effects, biochemical technique, mechanical technique