台灣稻米支出彈性值的檢驗

A Critical Test of Expenditure Elasticity of Taiwan's Rice Consumption

稻米需求的變動，受到一組複雜的因素所影響，因而不容易由其需求線的估計，得到有共識的支出或所得彈性值以及價格彈性值。尤其是支出彈性值的估計，更值得較得深入與廣泛的分析。因為，每人稻米消費量的變化，主要決定於支出的大小。所得或支出能力的增強使得食品的質與量均將加，也使稻米消費量發生變化。因之由支出額的變動趨勢，以及支出彈性的大小，即可粗略預測，每人稻米消費量的變化趨勢以及國內市場總需求量。如此，可由觀察台灣稻米產業調整能力的大小，而決定稻米進口自由化的幅度與快慢，或是當稻米進口自由化得時間表確定時，可由需求量的預測，來推估台灣稻米產業需做多大的調整。本文利用主觀的先驗信息，嘗試不同的計量處理，所得到的結論，傾向於支持稻米彈性為正值，且係數值在0.2至0.3之間的推論。此結論不同於一般利用自米消費量與支持肩負相關，所引伸的負支出彈性值。 Consumption demand for rice is influenced by a set of complicated factors. It is not easy to reach consensus on the estimates of income and elasticities. A rigorous evaluation of the magnitude of expenditure elasticity is even more important, because per capita food consumption depends on level of expenditure and per capita rice consumption is also adjusted to change in expenditure. A more reliable estimate of the expenditure elasticity of rice is useful in predicting the change in per capita rice consumption as well as change in total domestic rice demand. Reliable prediction of the quantity demanded, under given structural adjustment of rice production, is useful in making decision regarding the speed and magnitude of rice import liberalization. On the other hand, if the time table for rice import liberalization is given, one can determine the efforts needed for production structural adjustment. By adding a prior information to the standard regresstion model, this paper tends to support the view that expenditure elasticity of Taiwan's rice consumption is positive and the coefficient lies between 0.2 and 0.3. This is in sharp contrast with the popular view of negative expenditure elasticity, a typical result from a casual observation of negative correlation between expenditure and rice consumption.

Consumption demand for rice is influenced by a set of complicated factors. It is not easy to reach consensus on the estimates of income and elasticities. A rigorous evaluation of the magnitude of expenditure elasticity is even more important, because per capita food consumption depends on level of expenditure and per capita rice consumption is also adjusted to change in expenditure. A more reliable estimate of the expenditure elasticity of rice is useful in predicting the change in per capita rice consumption as well as change in total domestic rice demand. Reliable prediction of the quantity demanded, under given structural adjustment of rice production, is useful in making decision regarding the speed and magnitude of rice import liberalization. On the other hand, if the time table for rice import liberalization is given, one can determine the efforts needed for production structural adjustment. By adding a prior information to the standard regresstion model, this paper tends to support the view that expenditure elasticity of Taiwan's rice consumption is positive and the coefficient lies between 0.2 and 0.3. This is in sharp contrast with the popular view of negative expenditure elasticity, a typical result from a casual observation of negative correlation between expenditure and rice consumption.