As long as these two sets of data are compiled separately, it is very difficult for GDP data to maintain big errors over a long period. A corporation must have good data on itself, otherwise it cannot survive. In a modern economy, the vital role of interest rates and public expenditure makes timely and accurate economic data vital for policymakers. Otherwise, policy changes may come too late to move the economy in the right direction. For most developing countries, good national account data are difficult to come by, mainly because the informal economy is large and companies don't keep good books or may keep several books.
China faces such difficulties.
The short history of national accounting under the latter system makes China vulnerable to accusations that its data might be inaccurate. This was clearly the case last year. As East Asia's economies collapsed, China reported a very high growth rate and worsening deflation while at the same time companies reported poor earnings. All this caused doubts among some China-watchers about the quality of the reported data. Many skeptics cited a sharp slowdown in electricity consumption.