During the 1970's the bulk of the world's output came from Japan. The Chinese were culturing freshwater pearls in abundance, but they could not compete with the quality coming out of Lake Biwa in Japan. Akoya pearls were almost exclusively from Japan as the first Chinese akoyas appeared in the early 70's, but the quality was not good.
Lake Biwa became so polluted in the 70's that the tide changed and the bulk started coming out of China. This is the same to this day, except now the majority of akoya pearls come from China as well. It is widely known that most of the Chinese pearls make their way to Japan where they are worked and sold as Japanese pearls. The Chinese quality has gotten that good in nearly all sizes up to 8mm.
Michael
www.selectraders.co.uk