The crime and arrest rates were calculated from interim population estimates complied by the Population Research Unit of the California Department of Finance, based on preliminary census data. The report's individual sections cover crimes, arrests, local adult detention, and law enforcement personnel as reported to the State's Bureau of Criminal Statistics and Special Services. The crime and arrest data are based on information for the entire calendar year, while the information on local adult detention and law enforcement personnel are based on counts taken on the same day each year. Data showed that 1.8 million Index crimes were committed during 1980, compared with 1.7 million in 1979 and 1.4 million in 1974. The Index crime rate increased from 6,734 per 100,000 population in 1974 to 7,733 per 100,000 population in 1980. Crimes against persons increased 12 percent from 1970 and almost 47 percent from 1974. Arrests rose from 1.4 million in 1974 to 1.6 million in 1980. Felony arrests increased by 4 percent and misdemeanor arrests increased by 7.8 percent from 1979 to 1980. Over 29,000 adults were in county and city jails and camps in the fourth Thursday in September, compared to over 25,000 on the same day in 1974. A total of 67,321 people were authorized full-time law enforcement personnel on October 31, 1980, compared with 62,020 in 1974. Tables and an appendix presenting population estimates and statistics on adult and juvenile arrests by category are presented.