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Abstract
By now new modern rice varieties (MVs) with multiple pest and disease resistance have completely replaced early
MVs, such as IRS and IR8, except in a few areas of Asia. This study attempts to identify the changing impacts of
'first-generation' and 'second-generation' MVs on productivity in rice farming by estimating the yield function, while
correcting selectivity bias arising from the choice of varieties. For this purpose, we used farm-level survey data
collected for eleven cropping seasons in Central Luzon in the Philippines from 1966 to 1990. We found that while
the yield advantage of first-generation MVs over traditional varieties was limited, the yield-increasing effect of
second-generation MVs over first-generation MVs was highly significant. In particular, the adoption of improved
MVs significantly contributed to yield growth under the irrigated condition and during the dry season. Thus, we
conclude that the Green Revolution would not have been revolutionary without the development and the diffusion
of second-generation MVs with multiple pest and disease resistance.