Kristin Schwab

Technology means companies know more about shoppers than ever.

But in reality, retailers have always been quietly collecting data on us.

It's a practice as old as commerce itself.

Joseph Turow is author of The Voice Catchers, how marketers listen in to exploit your emotions, your privacy, and your wallet.

Business owners would keep notebooks on what kind of clothes you wore or who your friends and family were.

The difference is, back then, a shopkeeper had to guess if a woman's baby bump was indeed a baby bump.

Now a retailer knows the instant she adds prenatal vitamins to her cart.

He says a lot of consumers have no idea surveillance pricing is happening.

How common this kind of practice is, no one really knows.

But retailers are watching us closely, often for surveillance discounting.

Here's a coupon for being a member or 10% off that immersion blender sitting in your cart.

It's why, as a consumer, it's more difficult than ever to figure out if you're getting the best price.

Garrett Johnson is a marketing professor at Boston University.

He says if you want to compare prices, you kind of need to hide.

But are we really going to do this dance every time we buy something as mundane as toothpaste?

We'll be right back.

I decide to shop for toothpaste on Walmart.com on two different browsers.

On one, I'm signed into my account, which has my information.

On the other, I'm anonymous, but add my shipping address for exact location comparison.

Scrolling, scrolling, scrolling.