I've been meaning to post this, from the Cleveland Fed's latest edition of Economic Trends, for awhile.
In 1995, China pegged its currency, the renminbi, to the U.S. dollar at approximately Rmb 8.3 per dollar. This peg, however, tells us nothing about China’s competitiveness relative to the U.S. because it ignores price patterns. The real renminbi–dollar exchange rate adjusts the exchange rate peg for changes in relative inflation rates, thereby providing a clearer picture of China’s competitiveness.
On a real basis, the dollar has appreciated only 2.5% against the renminbi since the beginning of the peg; that movement cannot confer much of a trade advantage on China. The real exchange rate has, however, undergone some large swings.
Here's the picture.
The article concludes this way:
To be sure, China has many artificial barriers to trade and financial flows that help it sustain an overall balance-of-payments surplus, but the contribution of its exchange rate policies seems to have been overstated.