It's Curious City, where we take your questions about Chicago and the region,

and investigate, report, explore, from WBEZ.

I'm Curious City intern Mackenzie Crosson, and sometimes walking around Chicago, I've passed a bike rack and noticed a trace of something

sad, a toppled bicycle missing its front wheel, or a lonely cable lock lying on the ground.

The evidence of a bike theft. Our question asker Christina Perez has been there.

I've had a back wheel stolen, a front wheel stolen, a seat stolen, then I had a whole bike stolen.

Frustrated, she came to Curious City, asking, why are so many bikes stolen in Chicago, and where do all these stolen bikes go?

Now, bike theft is pretty common in big cities like Chicago. Not everyone files a police

report after their bike is stolen, so police data is just a starting point in understanding the

scope of the issue. But data obtained by Curious City show that Chicagoans report more than

4,200 bikes stolen every year on average.

Police only solve about 5% of those reported cases.

It's a problem.

While Chicago has been encouraging more biking to reduce traffic and pollution,

there's evidence bike theft actually works against those efforts.

So avid cyclists have taken it upon themselves to track down and recover stolen bikes.

They're volunteering their time to fill in the gaps that cities leave behind.

Brian Hans has been doing this work for 15 years.

He also co-founded a national bike registry system called Bike Index.

In addition to his regular day job, Hans' email inbox is typically filled with messages

about bike thefts around the country.

I easily do 100 messages a day of email, just supporting people, responding to people,

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