The economy will drift upward in 2012 as incremental changes take place in the housing market, with a divisive and uncertain policy environment the darkest cloud on the horizon, Fannie Mae said in an economic outlook Friday.

Doug Duncan, VP and chief economist with Fannie Mae, offered up the outlook from the GSE’s Economics and Mortgage Analysis Group.

“We’re entering 2012 with decent momentum, especially on the employment side, which is fostering positive household and consumer behavior,” he said in a statement. “Unfortunately, we expect this momentum to slow as we move through the first half of the year.”

Speaking via podcast, Duncan said that shrinking unemployment figures and stronger retail sales created a “decent” lift for the economy by yearend 2011.

The forecast signaled that real GDP finished last year with a 3.3-percent uptick, with the economy set to encounter approximately 2.3 percent in growth for the next two years.

If the forecast holds true, the housing market may not fare so poorly this year, either, and will likely lend movement to a dragging economy.

Fannie Mae said that total home sales could hit 4.7 million in 2012, reflecting a 3.5-percent boost from total sales, new and existing, last year. If trends continue, the forecast said that home sales could reach as many as 5 million come 2013.

Home prices may have fallen 4.6 percent lower in 2011 than figures seen from the year earlier, and could dip by 1.1 percent for 2012, with median new purchases falling from $223,000 on average to $218,000.

The mortgage origination channel varied by turns deep and southerly, with Fannie Mae saying that originations will likely plummet from $1.36 trillion to $1.01 trillion next year.

Figures for home loan purchases may offset the other numbers, with predictions that these could climb from $464 billion last year to $471 billion this year.

Duncan said during the podcast that fiscal policy will matter as much if not more than economic activity in 2012.

“It’s going to be fiscal policy and other policy issues that will determine the degree of activity that businesses and consumers undertake” as consumers take less concern with debt crises abroad, he said.