98991114_rime_in_the_United_States_2006__Reason_for_Estimation
[Year] 2001 [State(s)] Illinois [Estimation Method] Valid Crime Index (Part I) counts were available for most of the largest cities (100,000 and over in population). For other agencies, the only available counts were generated without application of the UCR Hierarchy Rule. (The Hierarchy Rule requires that only the most serious offense in a multiple-offense criminal incident is counted.) To arrive at a comparable state estimate to be included in national compilations, the total supplied by the Illinois State Program (which was inflated because of the nonapplication of the Hierarchy Rule) was reduced by the proportion of multiple offenses reported within single incidents in the available NIBRS data. Valid totals for the large cities were excluded from the reduction process. [Reason for Estimation] 
The state UCR Program submitted complete data for only seven agencies within the state. Additionally, the state UCR Program was unable to provide forcible rape figures in accordance with UCR guidelines.
Table 01, Data Declaration - Crime in the United States 2006
Reason for Estimation