I am prepared to risk my reputation by predicting that, the field has been built, so if you just wait: it is coming to you soon (assuming you've got the brains to really mean a reduction in GDP not negative GDP).
The word recession stems from the word 'recede', which is to contract. The economy has yet to actually contract since 2001. Slower growth is still expansion, nevertheless.
I actually believe that even though slower growth is still expansion as you stock_trader say, it is still a problem in terms of development.
I have no rep, so I'll just say I have no idea what you mean by the diff between reduction in GDP rather than negative GDP. Given that, the following comes from the St Louis Fed, because I had just finished reading how GDP had fallen in the 4th quarter when I read the last couple pages of this thread, and had to make sure I wasn't living in some weird alternative universe: Latest Observations: 2007-04-01 11491.4 2007-07-01 11625.7 2007-10-01 11620.7 (lower!!! really!!!) 2008-01-01 11646.0 2008-04-01 11727.4 This is real rather than nominal, of course. Source: http://research.stlouisfed.org/fred2/series/GDPC1?cid=106
Negative gdp would imply that there was negative production. So balance of payments if frequently negative but gdp ... is it ever negative? Recession requires two quarters of declining GDP (common definition). Depression requires 4 quarters (by one potential definition at least).