GDP can be derived from production, income, and expenditures; in theory, there is consistency between the three measures of GDP, which is termed the equivalence of three measures. However, in practice, because of the wide disparity of GDP data sources and the difficulty of avoiding survey errors and statistical omissions, it is nearly impossible to achieve equivalence between the results for the three measures. The UN's system of national accounts 2008 (2008 SNA) consequently notes the extreme difficulty of achieving the equivalence of the three measures in practice. In reality, statistical discrepancy (SD) will exists between the results for each measures; if any certain components of GDP is taken as an balancing item contains a statistical discrepancy, this will distort statistical results for that component.
In view of the foregoing, on August 20, 2009 the 206th Committee of National Accounts decided that the quarterly and annual production aspect of Taiwan's GDP shall express the SD, and income data shall be compiled in conjunction with production data, so that it will simultaneously express SD; and this approach should be retroactive to 1981.