Looking back at 2009, Gallup has singled out two trends: a growing percentage of Americans who identify themselves as conservatives and a decline in the percentage who identify themselves as Democrats.

Forty percent described themselves as conservatives last year, compared to 36 percent who said they were moderates and 21 percent who called themselves liberals. In 2008, conservatives and moderates were tied at 37 percent each, with liberals at 22 percent. Between 1992 and 2002, moderates reigned as the largest ideological group.

While the percentage of independents who considered themselves to be moderates held fairly steady in the low- to mid-40s during the last decade, the percentages of Republicans and Democrats who described themselves as moderate declined. Forty-four percent of Democrats were in the moderate camp in 2000 compared to 39 percent last year, and 23 percent of Republicans said they were moderates, compared to 31 percent in 2000.

Gallup's findings point to increasing polarization between Republicans and Democrats. The number of Democrats who considered themselves as liberals grew during the decade from 29 percent in 2000 to 38 percent last year. The percentage of Republicans who identified themselves as conservatives grew from 62 percent in 2000 to 71 percent last year.

As far as party identification, the number of those who said they were Democrats dropped below 50 percent for the first time since 2006. Forty-nine percent identified with the Democratic Party and 40.7 percent with the Republicans. The Democrats had started out the first quarter of the year with 51.7 percent of Americans in their camp, but that declined over the balance of 2009.