30年来长武县耕地数量与农业经济发展计量关系分析

Econometric analysis of relationship between quantity of cultivated land and agricultural economy in Changwu County in past 30 years

针对长武县近30年来农业经济快速发展和耕地数量锐减的现实,通过建立向量误差修正模型,运用脉冲响应函数、方差分解方法,对1980—2010年长武县耕地数量与农业经济数据进行计量关系分析,探索二者间的互馈效应。结果显示,农业经济受耕地数量减少的影响效应为正但不显著,近30年的脉冲响应均值仅为0.8,10年尺度上分别为0.4、0.8、1.6。而耕地数量受农业经济发展的影响效应为负,并随时间发展该负效应持续增强,10年尺度上均值分别为-0.3、-0.9、-2.8;30年来长武县耕地资源的变化并未对农业经济的发展有显著促进作用,其时期内最大贡献率仅为22%。而耕地数量减少主要受农业经济发展的影响,后者对前者的贡献率时期内从最大值88.9%稳定到78%。表明耕地数量减少在促进农业经济发展上存在过度损失,农业经济的发展是耕地数量减少的主要原因。发展农业经济亟需挖掘社会其它要素的作用,以保证耕地数量的持续稳定,避免不合理利用。

The agricultural economy of Changwu County has advanced rapidly over the past 30 years, while the area of agricultural land has declined at an＂ amazing speed during the same period. In this study, an attempt was made to quantify the relationship between the amount of farmland and agricultural economy development in Changwu by establishing Vector Error Correction Model （VECM） and in combination with Impulse Response Function and Variance Decomposition. The results indicated that, a positive but slight effect of farmland reduction on agricultural development was identified. The average impulse response values were 0.4, 0.8 and 1.6 for the periods of 1980--1990, 1990--2000 and ：2000--2010 respectively, and 0.8 for the entire 30 years. On the other hand, the effect of agricultural economy development on farmland amount was found negative, and tended to intensify with time. And the average impulse response values were - 0.3, - 0.9 and - 2.8 respectively. The change of farmland resources did not seem to contribute significantly to the advancement of agricultural economy, with only a maximal 22 % of the contribution from farmland change. While farmland decline was greatly influenced by agricultural development, and a peak 88.9 % of total decrease in farmland was triggered by agricultural economy factor. Thus, it is urgent to find out other factors that could boost the local agricultural economy and preserve the limited farmland resource for the purpose of food security.