By now, you’ve probably heard of Dollar Shave Club.

From that video in 2012, to selling razors to millions of customers, to its acquisition by Unilever for $1B last year, founder/CEO Michael Dubin and the rest of the Dollar Shave Club team has executed incredibly well on many dimensions. They’ve made quality razors and blades much more affordable for consumers. They’ve built a brand that people love, that speaks authentically, and connects at an emotional level. The team has worked very hard to launch new products, improve margins, spend money effectively on advertising, and more. But there is one key element to the business that has made it so successful:

Subscription.

Dollar Shave Club built a direct-to-consumer subscription service for razors and other bathroom products. The company was projecting over $200M in revenue last year when it was acquired. And the retention in its subscriber base was the key reason for the company’s ability to make its unit economics work, and why it was such an attractive asset for an acquirer like Unilever.

What many people may have over-looked about the power of Dollar Shave Club is the power of subscription.

Take a look at the customer retention cohort data below screen-shotted from Second Measure, a service that uses anonymized credit card transaction data to gain visibility on the performance of public and private companies. The percent figures correspond to the % of customers that transact in any given month (denoted by the number at the top of the tables). For instance, the top left % number, 69%, indicates that in the median monthly group of customers, 69% come back and transact in the first month after they initially made a purchase.