SINCE PORTLAND began grappling with a housing and homelessness emergency in October, a few numbers have popped up again and again.

There's 1,887—the estimated number of unsheltered homeless people who live in Multnomah County. Or 3,801—the estimated number of people in the county who meet the federal government's definition of homeless.

And of course there's $30 million—the amount, split between the city and Multnomah County, that officials have said will put us on track to cut homelessness in half.

Here are some numbers that haven't appeared: Since 2005, the City of Portland's spent nearly $850 million on affordable housing and homelessness prevention. That's an average of $70.6 million every year, pulled from a variety of sources.

Yet, as the Portland City Budget Office (CBO) notes in an interesting new analysis, the local homeless population is only around 200 people smaller than a decade ago, and we're hurting badly for affordable housing. 

"Many people wonder why, after hundreds of millions of dollars in investments and a coordinated strategy to address homelessness and affordable housing needs, the problem persists," the CBO wrote in its newly released review of the budget that the Portland Housing Bureau has requested for next year.

The answer to that question is complex, and the city's done a lot of good with its $850 million. But the huge river of cash that's been channeled toward housing and homelessness in recent years rarely, if ever, comes to light. And it's another number we should be talking about.

The CBO's review is a careful and critical look at the budget requests, delivered in a year that the bureau has a relatively free hand. The housing bureau's $153 million proposal is more than double its average budget over the past 12 years. The $40 million it's seeking from the city's general fund is more than 2.5 times the 12-year average.

That request has real momentum—even as Portland also looks for money for parks, cops, and roads. After all, the city needs 23,845 more cheap units, according to the housing bureau. This really is an emergency, and it deserves serious resources.

But the CBO's cautionary take is worth city council's attention. Analysts are finally forcefully saying what they've quietly urged since an emergency was declared: If Portland's going to spend this money, it better make sure it's working. The CBO wants clear goals for housing money, and it wants the city to rigorously track those goals.

And the office says officials need to be honest about how much funding will be required to slash homelessness to the levels they propose. More and more people are becoming homeless every day, the budget analysis notes—meaning the $30 million price tag might already be an understatement. And even if it's not, the report says more like $73 million is needed over a course of three years.

Importantly, the city's fiscal minders aren't suggesting that the city shouldn't spend historic amounts to curb this crisis. They just want officials to ensure that, when we pony up that next $850 million, it's going to get the job done.