• 2010 Report
• 2000 Report
• 1990 Report
• 1980 Report
• 1980-2010 Change
• 1990-2010 Change
• 2000-2010 Change

The population of Cook County, Illinois was 5,253,655 in 1980. The adherent totals of the religious groups listed above (2,967,455) included 56.5% of the total population in 1980.

^* In an effort to better match the ASARB standards for adherents, a few religious bodies changed the way their adherents were reported in 2010, including the Catholic Church, Amish groups, Friends groups, Jewish groups, the Church of Jesus Christ of Latter-day Saints, Non-denominational Christian Churches, and the United Methodist Church. This change does not affect any of the data in the newly released 2010 U.S. Religion Census: Religious Congregations & Membership Study. In fact, the data for these groups are now more comparable to that of other bodies than it was in previous decadal reports.

However, the change in methodology can distort assessments on growth or decline between 2000 and 2010 for each of these groups. County-level 2000 data using the new methodology are not readily available. ASARB staff has adjusted some 2000 county-level adherent statistics to allow for a more accurate picture on growth or decline. The revised maps and charts are now available on-line at www.usreligioncensus.org for those who are interested in these trends.

Source

2010 data were collected by the Association of Statisticians of American Religious Bodies (ASARB) and include statistics for 236 religious groups, providing information on the number of their congregations and adherents within each state and county in the United States. Clifford Grammich, Kirk Hadaway, Richard Houseal, Dale E. Jones, Alexei Krindatch, Richie Stanley and Richard H. Taylor supervised the collection. These data originally appeared in 2010 U.S. Religion Census: Religious Congregations & Membership Study, published by the Association of Statisticians of American Religious Bodies (ASARB). [More information on the data collection]

^†The adherence rate provides the number of adherents of a particular group per 1,000 population. For example, in 2010 the Episcopal Church had an adherence rate of 7.6 in Autauga County, Alabama. This means that about 8 out of every 1,000 people in Autauga County were Episcopalian.