In the U.S. economic growth measures are always presented at annual rates. There is no magic to using annual rates, but it is the convention. This is why it is infuriating to see the NYT use quarterly growth figures in an article reporting on Europe's growth rate for the fourth quarter of 2009.
The use of quarterly growth rates will undoubtedly confuse the vast majority of readers. It is a simple matter to convert France 0.6 percent quarterly growth rate in the 4th quarter to a 2.4 percent annual rate. Readers who read through this article quickly are unlikely to make this calculation and instead walk away confused about European growth rates. The reporter should have the time to make this simple adjustment.