More Guns, Less Crime is a book by John Lott that says violent crime rates go down when states pass "shall issue" concealed carry laws. He presents the results of his statistical analysis of crime data for every county in the United States during 29 years from 1977 to 2005. The book examines city, county and state level data from the entire United States and measures the impact of 11 different types of gun control laws on crime rates.