The Producer Support Estimate (PSE), developed by OECD, may not be a reliable measure of support for Korean farmers. The current reference price for Japonica rice, the Chinese c.i.f. price is used to compute Korean PSE. However, current literature suggests that the world Japonica rice price will increase significantly under complete liberalization scenario, which implies that the current PSE for Korea is overestimated. Using @Risk, the distribution of possible reference prices is estimated and it is used to estimate the distribution of PSE measure. The result implies there is 3 to 10% estimation error, by changing the reference price for rice only, which may not be acceptable.