Amazon remains an e-commerce company at its core, but like any tech giant, it’s put its fingers in many other pies over the years. Some of its attempts have been disasters. Others are bona fide smash hits.

The biggest surprise, though, continues to be the Amazon Echo — the family of smart speakers that, along with its Alexa voice assistant, has steadily put Amazon in a leading position within the Internet of Things and the burgeoning consumer market for artificial intelligence.

As this chart from Statista shows, the Echo only gained momentum in 2016. Device sales have more than doubled year-over-year, while the amount of “skills” third-party developers have built for Alexa has risen by thousands within the span of a few months. And because Amazon ties the device so tightly with its retail site, Echo buyers also tend to pump more money back into the company’s core business.

All of this should be on the conservative side once the year comes to a close, too — that 5.2 million figures doesn’t include holiday sales, and Amazon said on Tuesday that the diminutive Echo Dot has been the highest selling device on since November 1, with the standard Echo in the top four. All of this comes despite the Echo only being available in the US, the UK, and Germany.

It’s not all sunshine and rainbows, though: A recent police search warrant for an Arkansas man’s Echo recordings has served as a reminder for the privacy concerns inherent to devices like this, and on a functionality level, we’ve found that Alexa itself still needs plenty of work. The latter point would explain why Echo owners mostly use the device for basic tasks.

amazon echo 2016 chartStatista

Disclosure: Jeff Bezos is an investor in Business Insider through his
personal investment company Bezos Expeditions.