Are there a lot of inground swimming pools in Michigan?

If you were to venture a guess as to the number of inground swimming pools in the 5 counties surrounding Detroit (Wayne, Oakland, Macomb, Washtenaw, and Livingston), what would you guess it is?

I was asked this question and that got me to  thinking about the whole state of Michigan and how many inground swimming pools there are. I wonder what everyone thinks?  Do you have any idea? 5,000, 10,000, 25,000, 50,000 or maybe more. Send in your guess while I research it. I do know the 5 counties answer so guess that also.