The ProPublica Illinois and Chicago Tribune investigation “The Tax Divide” has been selected as one of five finalists for the Richard H. Driehaus Foundation Awards for Investigative Reporting. Sponsored by the nonprofit watchdog organization Better Government Association, the award honors some of the best government-related investigative reporting in the Midwest.

“The Tax Divide” examined Cook County, Illinois’ unfair property tax assessment system. For decades, controversy had swirled around the assessment system in Cook County, the largest in Illinois. Residents and business owners had suspected their property taxes were based on inaccurate assessments, but the process is so opaque and convoluted that few people understood it.

Lead reporter Jason Grotto — who started the project as a Chicago Tribune staff writer and continued his investigation after joining ProPublica Illinois — studied the arcane system for two years, exposing widespread inequities and egregious errors in assessments. In his exploration of problems with both residential assessments and commercial valuations, he illuminated a system that punished small businesses and poor homeowners, while giving the wealthy unsanctioned tax breaks and lining the pockets of politically connected tax attorneys. ProPublica Illinois data reporter Sandhya Kambhampati and Chicago Tribune reporter Ray Long also contributed to the work.

After the series, the inspector general for Cook County launched an investigation, and the county board president ordered a study of residential assessments by an outside consulting firm. State and local lawmakers, concerned that the property tax system favored those who supported Berrios politically, introduced legislation to limit campaign contributions to the assessor. In the Illinois primary election last month, Berrios lost his bid for reelection.

Winners will be announced on May 1. Learn more about this award here.