There are a number of reasons for this, namely, ubiqutous pre-mortem imaging with improved techniques and detection of disease pre-mortem, lack of payment/reimbursement, more out of hosptial deaths and decreased number of physicians trying to obtain consent.  I have seen the autopsy rate at some hospitals in my career as low as 8%.  What is not clear to me is why/how JCAHO does not cite for these kinds of findings and why more is not done in clinical medicine to obtain consent for what is still widely considered the "gold standard" in medicine for clinicopathologic correlation and assessing effects of therapy and natural history of disease.

It is said the Virchow himself performed over 50,000 autopsies.  I can't imagine doing that many, but these numbers are paltry.

The Wall Street Journal (8/4, Hobson) "Health Blog" reported that CDC statistics show that in 2007, autopsies were performed on 8.5% of deaths, compared with 19.3% of deaths in 1972. CDC scientist Donna Hoyert says this may be due to medical professionals believing that autopsies are unnecessary due to modern technology. However, doctors point out that autopsies can contradict imaging findings, and alert families to genetic conditions. The report also notes that the Joint Commission has removed a rule that hospitals must perform autopsies on 20% to 25% of deaths. 

HealthDay (8/4, Preidt) reported that "in 1972, deaths due to disease accounted for 79 percent of autopsies, while deaths due to external causes such as injury or murder accounted for 19 percent. By 2007, the respective percentages were 46 percent and 50 percent, the investigators found. External causes of death -- including murder, accidental injury, suicide or undetermined cause -- accounted for nine of the 10 most frequently autopsied causes of death in 2007." The report also showed that "while the number of deaths among older people increased from 1972 to 2007, autopsied deaths were increasingly concentrated in the one to 34 and 35 to 64 age groups." WebMD (8/4, Hendrick) also covered the study.

http://blogs.wsj.com/health/2011/08/04/the-incredible-shrinking-autopsy/?mod=WSJBlog&mod=WSJ_health