The shadow inventory has some analysts raising questions on housing's 2012 prospects.

The National Association of Realtors (NAR), spurred on by a better-than-expected early spring homebuying season, has modestly upgraded its economic projections for the next two years to better reflect the current economic climate – though as one analyst has pointed out, those projections may come with a conspicuous omission, even amongst like-minded analyses from fellow trade groups.

But first, NAR’s data. Released earlier in the week by Lawrence Yun, the association’s chief economist, the 2012 Economic and Housing Outlook included optimistic readings on a number of important housing statistics, among them existing-home sales, which NAR is estimating will grow from 4.26 million in 2011 to 4.71 million in 2013; new home sales, which could increase from 304,000 to 530,000; housing starts, which could rise from 611,000 to 960,000; and existing home values, which NAR predicts will increase from $166,100 to $172,000, an appreciation of 3.5 percent.

Promising numbers, to be sure, but the blog for The Regional Economics Institute at Colorado State University, in a possibly prescient post, highlights a dimension to the housing market that could throw a little bit of mud on NAR’s projections.

For its analysis, the post looked at two decidedly different graphs on housing inventories buried in NAR’s full analysis. The first graph, which showed visible housing inventory, rose substantially during the boom years, and has gradually (but inconsistently) declined since then.

“Lately, we see visible inventory is still high, but declining,” the post read. “This gives some suggestions that the market is moving back to equilibrium, and prices might start moving up again.”

The second graph, though, which shows shadow inventory, complicates the inventory scenario. Unlike the visible inventory graph, the shadow market remained low throughout the boom years, only to skyrocket after the boom subsided and the economic recession kicked into full gear in 2008. Even though the shadow inventory has declined somewhat the last couple years, the post does mention the problems a lingering shadow market can pose for a housing recovery.

“Until all of this inventory overhang clears, prices will likely remain stagnant, new building relatively rare, and the housing market far from where it needs to be,” the post read.

Yet, even with that knowledge, NAR is not the only notable trade association predicting solid things for housing and the economy going forward. In a separate, independent study, the National Association of Home Builders also saw encouraging signs in the unseasonably warm spring, and predicted good things going forward.

“All indications suggest that the key spring selling season has gotten off to a solid start,” the association stated. “Most builders and Realtors report significant gains in buyer interest and sales. Moreover, the gains are organic rather than incentive induced.”

So how do you see it? Will the shadow inventory continue to pose a problem going forward, or have we turned a new leaf with an unexpectedly strong spring?