Lawrence and the rest of country continue to see decreases in violent and property crime, according to preliminary 2011 statistics.

In tight economic times, crime usually shoots up, not down. That’s why the decreases are “puzzling and heartening,” said Richard Rosenfeld, a criminologist at the University of Missouri-St. Louis. “I’d be happier if I could figure out why.”

2011 also marks the third straight year without a murder in Lawrence.

If the second half of 2011 follows Lawrence’s trends for the year:

• Violent crime, including murder, rape, robbery and assault, will decrease 18 percent, from 413 offenses to 338, according to numbers provided by the Lawrence Police Department.

• Property crime, including larceny, motor vehicle theft, arson and burglary, will decrease 5.5 percent, from 3,841 offenses to 3,628.

Last week, the FBI released its Uniform Crime Report, which measures offenses reported to law enforcement, for the first six months of 2011.

The report showed:

• Violent crime decreased 6.4 percent in 2011 as compared with the first six months of 2010.

• Property crime decreased 3.7 percent.