SPRINGFIELD, MASS. ? Improvements in emergency care over the past 40 years have helped to dramatically lower the death rate among assault victims by nearly 70 percent and, in the process, decrease the nation’s murder rate, according to a new study.

“People who would have ended up in morgues 20 years ago, are now simply treated and released by a hospital, often in a matter of a few days,” said Anthony R. Harris, a sociology professor at the University of Massachusetts at Amherst, who headed the statistical study with Harvard Medical School that looked at crime data from 1960 to 1999.

The study was published in the May issue of Homicide Studies, a quarterly interdisciplinary journal devoted to criminology.

Deaths from criminal assaults dropped almost 70 percent over the 40 years, with annual declines of 2.5 percent for firearm and knife assaults and 3.5 percent to 4 percent for other assaults, including poisoning and arson, the researchers found.

In 1960, police nationwide recorded 9,110 homicides and 154,320 aggravated assaults. That translates into 5.1 homicides per 100,000 people and 86.1 assaults per 100,000. Researchers found 5.6 percent of those assaults ended in death.

In contrast, police in 1999 recorded 15,522 homicides, a rate of 5.7 per 100,000, and 911,740 aggravated assaults, a rate of 334.3 per 100,000.

But only 1.67 percent of the 1999 assaults ended in death.

The researchers noted that there was an uptick in deaths from assaults in 2000 and 2001 and said they were studying it.

Their study of the 40-year period credited a variety of medical advancements in the improved death rate: the development of 911 services, rapid stabilization and transportation of trauma victims, better training for emergency medical technicians and increased numbers of hospitals and trauma centers, particularly in rural areas.

Using statistical analysis, the researchers figured that without medical advances, 45,000 to 70,000 homicides would have been recorded annually nationwide.