These are the stores where the most people use their iPhone to pay

New analysis suggests that drugstore Duane Reade and grocer Whole Foods have been the most successful brick-and-mortar stores at getting customers to embrace Apple Pay - a technology that allows Apple users to pay with their phone or watch.

But the usage rates even at the best brick-and-mortar retailers lag behind services with popular mobile apps, according to data analysis from TXN, a consumer spending analytics app.

They found that the total number of monthly Apple Pay transactions grew by 50% year-over-year in their sample, although it still "accounts for a fairly small percent of all credit card transactions," according to the analysis.

TXN derived its analysis from its research panel, which has over 3 million payment cards, according to CEO Jonathan Wolf.

TXN's participants let the company essentially see their credit card statements in exchange for incentives. One TXN analyst figured out that some banks label Apple Pay transactions, so they used that to chop their data into Apple Pay and non-Apple Pay credit card transactions.

Overall, Wolf sees a "success story" based on growth for Apple Pay in this data. "If you offer a payment option while shopping on your phone, it's a real thing," he said.

"Five years ago the ability to pull my phone out of my pocket and pay did not exist." Since then, he said, "I've gotten faster and faster on the draw. There's a point where it's actually faster to pull out your phone."

Apple Pay, a way to pay for goods with an iPhone or iPad, was launched in late 2014 along the iPhone 6. Since then, Apple has expanded it to the web, to Mac computers, and has signed up hundreds of banks.

But Apple does not share a lot of Apple payment data. Most recently, last summer it unhelpfully said that Apple Pay has "tens of millions" of monthly users.

So the best way to get an idea of who and how people are using Apple Pay comes from analytics companies like TXN. You can read their full report here.