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Coefficient of dispersion, price-related differential, first-pass, second-pass, assessment level, effective tax rate ... I’d use these terms in meetings with my editors, and I could feel my own eyelids getting heavy.

For about 2 1/2 years now, I’ve been reporting on the Cook County property tax assessment system, uncovering inequities and explaining them to readers. At times, the work has been mind-numbing, with long stretches when I was lost in the weeds. But one thing was certain: Behind all the technical terms and the statistics was a story about the simple concept of fairness.

In many ways, the assessor’s office is a black box. Not even attorneys who have worked in the field for decades understand how the office derives values. And Cook County Assessor Joseph Berrios has refused to make that information public. My work, to some degree, involves poking holes in the box so we can shed light on how the office operates. My story this week on commercial and industrial assessments is the latest, following work I did on residential assessments for the Chicago Tribune.

In the early days of reporting these stories, I found Illinois Department of Revenue studies that suggested the property tax assessment system was deeply unfair. I wanted to determine if the evidence supported that assertion and proved the system was broken. As my reporting — and my work with colleague Sandhya Kambhampati — progressed and I learned more, I began to see how those with the least were paying more than they should while the wealthy paid less.

At a time when income inequality has grown to staggering proportions in our country, I came to see that the property tax system aggravated those disparities. Many of those who benefited were political heavyweights who also work as property tax lawyers.

How could I present this information in a way that would move readers and, perhaps, drive change? I knew the key was getting behind the numbers and finding the people who were harmed by the system. Their compelling stories fueled the narrative as we presented the nuts and bolts of this arcane system and our investigative findings about it.

I found people like Brenda Doyle, owner of Sweet Pea Academy day care, in the Auburn Gresham neighborhood on the South Side. She ran the day care with her husband, Larry, and daughter Jamilah. Sweet Pea is exactly the kind of small, family-owned business that should get a fair shake. Instead, its tax bill was far higher than it should have been, which made it hard for the family to stay afloat. The story about the Doyles’ business was similar to ones I discovered when reporting on residential assessments for the Chicago Tribune. For that project, I found a block in North Lawndale where nearly every property was overvalued. Many of the people I met grew up in their homes, having inherited them from their parents, and now are having trouble paying their property taxes because they were overvalued. People like Joan Clark, who struggled to pay the property tax bill on the home she grew up in because it was overvalued by 40 percent. She told me she was worried about losing her house.

These are the people who matter. They are why we worked so hard to shine a light on this issue.