In 2019, 51.3% of US households will be Amazon Prime members, according to our latest forecast—that’s about 5.2 million more households than last year.

Prime's growth will be fueled by lower-income households and consumers attracted to the platform's new offerings. Expanding beyond the flagship Prime benefit—fast or free shipping—Amazon continues to diversify its value to customers.

“New membership is driven by the company’s continuous expansion of Prime product categories, like groceries, apparel and pantry—as well as new options for media consumption, like books and video games,” said Martín Utreras, eMarketer's vice president of forecasting.

And subscribers can also take advantage of Prime’s Amazon Household. This service is a no-brainer for bigger families, as it offers Prime benefit sharing via linked accounts for up to two adults, four teens (ages 13 to 17) and four children (12 and younger). The service also offers parental controls for media, as well as household-specific discounts on products like diapers and baby food.

But all this comes at a cost. In May 2018, the company raised its annual membership fee to $119—only the second increase in Prime's history. (The first was in 2014, when it increased from the debut price of $79 to $99.)

To soften the blow of a higher cost, the company has introduced various payment plans and special discounts, including a $12.99/month option, an annual student membership fee of $59, and a $5.99/month fee for those on government assistance.

These offerings are attempts to capture and retain a wider range of consumers. "Amazon’s flexible discount strategy shows it's trying to attract the long tail of the consumer market,” Utreras added.

That makes sense, because Prime users spend an average of $1,400 per year on Amazon vs. the $600 non-Prime members spend yearly, according to an October 2018 study from CIRP.