The UCR involves voluntary participation from local police departments who report the crimes known to and recorded by them. However, not all crimes committed are discovered; not all crimes discovered are reported; and not all reported are recorded. The majority of states employ UCR programs in which local departments are required to report. During the 1980s, 98% of metropolitan statistical areas (MSAs), 94% "other" cities, and 90% of rural areas reported to the UCR. The Census Bureau determined that 97% of the population had been covered by this report. The Uniform Crime Report contains Part I and Part II crimes. Part I are index crimes, or major felonies reported to the police that have been selected for special analysis because of their seriousness, frequency, and likelihood of being reported. Index crimes include: murder and non-negligent manslaughter, burglary, forcible rape, larceny/theft, robbery, motor vehicle theft, aggravated assault, and arson. Part II are non-index crimes such as simple assault, vandalism, gambling, and drunkenness.
The crime rate is represented as the number of crimes per unit of population. This enables control of the population size and allows for fair comparison. However, the crime index is un-weighted, meaning that each offense is summed and given the same weight as all other offenses. The crime rate is the total number of seven of the original index crimes per 100,000 population.
Number of index crimes
Crime rate = Population x 100,000
Some caution should be taken in reference to...