Data released Tuesday from securities research firm Consumer Intelligence Research Partners estimates that Amazon.com Inc. now has 80 million Prime customers in the United States, up 37.9% from 58 million this time last year.

That 80 million figure comes from a survey of 500 U.S. shoppers who bought on Amazon during the first quarter of 2017 and represents about 60% of total Amazon shoppers, according to CIRP. According to the U.S. Census Bureau, there are 257.6 million people age 15 or older living in the United States and 125.8 million households, meaning that 31.1% of U.S. residents 15 and older or 63.6% of all U.S. households have a Prime membership.

Prime is Amazon’s annual membership program that offers such perks as free two-day delivery on over 40 million Prime-eligible items as well as perks such as access to movies and same-day delivery in a growing number of markets through the Prime Now service. Shoppers can sign up for a $99 annual membership or a $10.99 monthly membership, an option that Amazon has offered since April 2016.

Source: Amazon Prime members number 80 million in the US, up 38% year over year