Abstract
The world's three major grains were maize, rice and wheat. The yields of these grains increased by agriculutural revolution. But the self-sufficiency rate for grains ( SSRG ) differed in countries. North American Free Trade Agreement was concluded in 1994. The growth of imports has hada significant impacts on Mexico's SSRG. The negotiation of trade liberalization will have enormous implications for SSRG of Japan. We needs more effort to the increase of SSRG in Japan.
