The largest manufacturer of matcha in Japan is likely Aiya Seicha based in the Nishio region of Aichi Prefecture. However, tracking matcha production is actually a bit difficult. The Ministry of Agriculture, Forestry and Fisheries (MAFF) only keeps track of production of agricultural crops, in other words the tencha leaves used to make matcha, and then only the pre-refined tencha (aracha or rough tea leaf state) which will weigh slightly less after stems, etc., are removed before grinding into matcha.
Finally, complicating the matter, in 2009 the MAFF also began grouping all shaded teas together (gyokuro, kabusecha and tencha) because while we say kabusecha is shaded for 2 weeks, gyokuro for 3 weeks, and tencha for 4 weeks, in actuality the period of shading is a gradation depending on weather, location, etc.
However, it seems that Aichi Prefecture itself continues to track production of tencha nationally. Here are the statistics for tencha production:
|2013||2243||770||479||647||347 (Nara: 125, Mie: 207)|
|2014||1969||818||539||269||343 (Nara: 120, Mie: 116)|
Aichi Prefecture documents from 2013 also breaks it down by 1st flush, 2nd flush and “other”, and out of Shizuoka’s 647 tons in 2013, 575 tons was “other” indicating low quality industrial grade matcha likely for products like matcha chocolate, ice cream, etc.
2010 data: http://www.pref.aichi.jp/cmsfiles/contents/0000050/50127/sankou.pdf
2013 data: http://www.pref.aichi.jp/cmsfiles/contents/0000073/73594/sankou.pdf
Japan Agriculture (national farmers’ cooperative) has more details on production in other prefectures: http://www.zennoh.or.jp/bu/nousan/tea/dekiru03.htm
2014 data: http://www.pref.aichi.jp/cmsfiles/contents/0000084/84241/sankou.pdf