On the link (or lack thereof) between solving murders and reducing their number

An article in the Houston Chronicle today laments the declining clearance rate for homicides, which in many jurisdictions are below 50%. Reports Yang Wang (no really, that's the reporter's name):

Some Houston-area communities are among 120 cities and counties across the state where 63 percent of murders or fewer are solved — falling short of the national average — according to a Houston Chronicle analysis of the FBI Uniform Crime Reporting database. The findings are based on cases reported by local agencies from 2004 through 2009.

For some communities, the problem is sheer volume: Too many murders, too many culprits and too many places to hide in a massive metropolis of nearly 6 million people.

For others, a lack of manpower, forensic crime labs and simple clues reduce the odds of finding a killer. The city of Galveston, for example, had just 32 murders between 2004 and 2009, but solved only 17.

San Antonio's Bexar County Sheriff's Office cleared just 39 percent of its homicides, Waco 56 percent and Odessa 52 percent, based on numbers the police agencies provided to the FBI.

But while murder clearance rates in some cities lag behind the national average, nearly 70 percent of the slayings in Houston get solved. In fact Houston, considering its size, is on par or better than most cities of its size.

But how much is enough? A 70 percent success rate still leaves 30 percent without answers. And the numbers provide little comfort to the families of victims across the region where 850 deaths have yet to result in arrests.

Even with its greater ability to solve these violent crimes, the Houston Police Department still had 550 unsolved murders; Harris County had about 170. At the same time, both agencies reported more than 1,609 homicides with suspects identified.

It's a strange conundrum that homicide clearance rates are declining nationally at a time when the numbers of murders are also going down. That means that the efforts of police and prisons - catching killers and taking them off the street - likely isn't the reason for the declining number of murders, though that's the traditional cause-and-effect paradigm that's portrayed in the media. Instead the reasons for declining murder rates are more demographic, economic and cultural than they are a result of improved police work.

But what is the reason for declining clearance rates? My theory is that society has come to use police too frequently to address social problems like alcoholism, drug abuse, child support, truancy, etc., or for revenue enhancement in the case of writing traffic tickets, instead of focusing on traditional crimes with actual victims. (Clearance rates for burglary are much, much lower even than for murder.)

It's simple, really: If all your cops are writing tickets, combing the streets for DWIs, busting penny ante drug users, chasing down truants, compiling photographic catalogs of graffiti, etc., those same cops aren't spending their time helping solve homicides. And Texas voters' anti-taxation sentiments mean local governments couldn't hire enough police to perform all these tasks, even if they wanted to do so. So the stuff that generates revenue (like writing traffic tickets) or that lends itself to political demagoguery (like graffiti and DWI enforcement ) gets prioritized over catching killers or burglars.

What do readers think explains declining homicide clearance rates? And if homicides are declining at the same time police are solving a lesser percentage of murders, what do you think accounts for the overall decline in recent years of homicides nationwide?