WASHINGTON (CNN) -- The U.S. violent crime rate declined 2.2 percent last year, continuing a decade-long downward trend in serious offenses, the FBI said Monday.All major categories of violent crime in the United States declined in 2004, bringing the rates of the most serious offenses, including murders, rapes, robberies and assaults, to a level 32 percent lower than those reported in 1995, the new figures show. The rate of property crimes -- such as burglary, larceny and auto theft -- declined 2.1 percent as well last year.The only category of violent crime in which the number of incidents rose was forcible rapes -- to 94,635 in 2004 from 93,883 in 2003, an increase of 0.8 percent. But accounting for an increase in population, the rate of forcible rapes dropped 0.2 percent.The 523-page FBI Uniform Crime Report is the final compilation and statistical analysis of crime data reported by nearly all state and local law enforcement agencies for 2004.The annual report offers no reasons for the trends, but the exhaustive statistical data provides criminologists and academics with raw material to examine.Experts have attributed declines in recent years to a variety of factors, including an aging population and harsher punishments such as mandatory sentences.In 2004, the number of violent crimes dropped 1.2 percent to 1,367,009 from 1,383,676 in 2003.One murder occurred in the United States every 32.6 minutes, and the murder rate dropped 3.3 percent to 5.5 per 100,000 people (16,137 offenses).The number of murder cases was down by nearly 400 from the previous year.The report said the number of murder victims and the total of suspects were both nearly equally divided by race. Most suspects were adult men using firearms, and about one in five murder victims was female.Last year there were 401,326 robberies, down about 13,000 from 2003, and the robbery rate dropped 4.1 percent to 136.7 per 100,000 people. Arrests were made in 62 percent of murder cases, 55 percent of aggravated assault cases, 42 percent of rape cases and 26 percent of robbery cases, according to the report.Almost 7,700 hate crimesThe FBI calculated 7,649 hate crimes -- cases in which offenders were motivated by bias. Of those cases, 53 percent of cases were based on race, 16 percent on religion, 15 percent on sexual orientation and 13 percent were based on ethnicity. Because of changes in reporting procedures, the FBI provided no statistical comparison to the previous year.Of single-bias incidents, the most -- 2,731 -- were described as anti-black, while 954 other cases were labeled anti-Jewish. Of the anti-homosexual cases, 738 were committed against men and 164 were against women. The FBI report also contained two special reports that examine juvenile drug violations and crimes against infants.The drug abuse report said the number of juveniles arrested increased over a 10-year period, from 159,000 in 1994 to 195,000 in 2003."Trends for overall arrests involving drug abuse suggest that this social problem shows no signs of abating," the report said.In 2003, the last year for which juvenile arrest data was available, nearly 163,000 juveniles were arrested for possession -- 127,000 of those arrests involved marijuana, and 14,000 involved cocaine or opium. Nearly 32,000 juveniles were arrested for the sale or manufacture of drugs, the report found.In what the FBI terms an "exploratory study," a review of data involving infant victims shows that between 2001 and 2003, there were 94 cases of murder including non-negligent manslaughter of infants under 1 year of age. Most of the offenses involved assaults -- 1,023 aggravated assaults and 1,404 simple assaults.There were also 215 kidnappings and 39 rapes.Most of the incidents involved relatives or someone the family trusted. The report said an infant is rarely the only victim but reliable information is difficult to collect."When incidents occur in private and the witnesses to such crimes either cannot speak for themselves or may be reluctant to speak because of a sense of loyalty to friends and family, it can be difficult for law enforcement to ascertain sufficient information during an investigation to have a case accepted for prosecution," the report concluded.