CHICAGO (CBS) — Murders in Chicago were down last year, but it’s a different story when it comes to the number of murders actually solved.

As WBBM Newsradio’s Steve Miller reports, the murder clearance rate – the number of homicides that were solved the same year – has slipped.

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LISTEN: WBBM Newsradio’s Steve Miller reports

“Forensic evidence may need processing time… so it stands to reason that an investigation may extend beyond a calendar year,” a police spokeswoman said.

But in 1991, for example, the murder clearance rate was 80 percent in Chicago – 927 murders committed, 741 solved.

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In the early 1990s as a whole, the rate was 72 to 73 percent.

By 2005, it had slipped to 42 percent.

Last year, it was 30 percent, meaning fewer than a third of the murders committed in 2011 were solved last year.

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If there’s any good news, the 2011 figure is slightly up from 28 percent in 2010.