What do bankers use isochrones for?

Confirm your numbers.

If you can point to a study that says "10% of white males between 18 and 24 go paintballing regularly" and then whip out isochrones that capture exactly how many white males are within a 15 minute isochrone, it takes arithmetic to determine what your likely annual capture of white males between 18 and 24 are. YOu certainly aren't guaranteed their business but you have a reasonable expectation that short of loyalty to somewhere else or personal animosity towards you, they're coming to you first.

With veen's help I was able to determine exactly how many likely consumers there were among any given location. More than that, I was able to determine how many consumers there were among our competition and then, thanks to the wonder of Washington State vital statistics data, calibrate how many births any given birth center *should* have vs. *did* have. This allowed me to not only get a good estimate for our own practice, but also see which practices were leading or trailing the statistical norm.

Finally, we were able to perform the same analysis on Los Angeles, my wife's old market, to demonstrate that she was outperforming the statistical mean by a factor of seven.

When you're able to say "this practitioner has historically outperformed the statistical mean by a factor of seven but will be profitable even if she underperforms the statistical mean by a factor of five" you have an easier time getting a loan.