The day Sacramento County officials disclosed they may have to lay off more than 1,000 employees to close the county’s $187 million projected budget gap, Standard & Poor’s downgraded the county’s credit rating from AA- to A+.

In its narrative explaining the downgrade, the credit agency pointed to “stress in local real estate values.” Specifically, the Standard & Poor’s analysis noted that assessed values for some 50,000 Sacramento County properties fell in fiscal 2008; in the current fiscal year 85,000 were downgraded, and the assessor estimates that 170,000 parcels will be downgraded in the coming fiscal year.

That represents a dip in values for about a third of the county’s 507,000 parcels.

In 2008, property taxes accounted for the largest share of the county’s general fund revenues, 19 percent. In 2010, assessed values are projected to be down by 9 percent.

Clearly, Sacramento County, like the rest of California, is feeling the impact of the housing collapse that has sparked a global recession. But it’s not the only issue affecting finances. Something more is at play here, and that is the fiscal black hole that this page has long termed the “uncity” – the urbanized portions of Sacramento County that exist outside the county’s cities.

Sacramento County’s “uncity” has shrunk in recent years with the incorporation of the new cities of Citrus Heights, Elk Grove and Rancho Cordova. Even so, a large percentage of Sacramento County residents, some 40 percent, continue to live in the unincorporated areas of the county, in communities such as Arden Arcade, Carmichael and North Highlands.

There’s a reason for this. Historically, some of the region’s largest employers, including the former Mather and McClellan Air Force bases and Aerojet, established their sites a considerable distance from the county’s main city of Sacramento. The county provided municipal services, primarily police protection, to the bedroom communities that grew up around those job centers. After the bases closed and Aerojet shrank, those outer-ring suburbs experienced serious decay. The cost of providing police and social services grew, but the amount of taxes generated in those communities plummeted.

The recession has exacerbated the structural imbalance that has long existed in the “uncity.” Standard & Poor’s analysis of the county’s fiscal outlook highlighted the problem: “The county continues to provide municipal-type services to the approximately 40 percent of residents living in unincorporated areas, a rate that is, in our view, still high in comparison with that of other California counties.”

In the past, the county has performed some accounting magic to balance its budget despite the fiscal drag from the “uncity,” including booking sales tax revenue before it arrived in county coffers, refinancing the jail and doing internal borrowing, among other things. But with the deepening of the recession, the county has run out of gimmicks.

In the short term, supervisors must make difficult and painful budget cuts, including layoffs.

In the long term, the economic crisis presents elected officials with a golden opportunity to create a more sustainable and economically vibrant county. They need to seriously consider shedding some of the county’s expensive municipal burdens permanently. They can do that by encouraging densely populated unincorporated areas to either form their own cities or attach themselves to existing cities.

So supervisors – if you want to save the county, there’s a good way to do it. Eliminate the “uncity.”