How Private Is Your Personal Health Data?

If there's one place that people still expect a reasonable amount of privacy, it's the doctor's office. But according to journalist Adam Tanner, maybe they shouldn't.

In the world of Google and big data, he explains every drug you're prescribed, every blood test, every step on the scale is all recorded. And that data has created a multibillion-dollar business — one where some of the most intimate data about us is aggregated and sold.

Tanner explains how this happens in his new book, "Our Bodies, Our Data: How Companies Make Billions Selling Our Medical Records."

Adam Tanner, writer-in-residence at the Institute for Quantitative Social Science at Harvard University and author of "Our Bodies, Our Data: How Companies Make Billions Selling Our Medical Records." He tweets @datacurtain.