Dive Brief:

• Owners of the Amazon Echo spent around 10% more on Amazon in the six months after they bought the voice-controlled speaker than before they had the device, with purchase frequency also growing 6%, according to data collected by NPD Group's Checkout Tracking purchase monitor cited by TechCrunch.

• NPD also found that Echo owners conduct about half of their total online spending at Amazon after they buy an Echo.

• The Amazon Echo supports a series of functions, including answering questions, playing music and controlling smart devices. The hands-free device has been available for about two years; about 1.6 million have been sold, according to BI Intelligence data cited by NPD.

Dive Insight:

Echo appears to be doing exactly what Amazon hoped, and what many analysts thought it was capable of doing — becoming a sale engine for Amazon, increasing sales by making it easier for those of us who are too busy, or think we're too busy, to do our online shopping the old-fashioned way (with our fingers).

Actually, the Echo's success begs the the question: Is it because of the Echo's engagingly simple design and utility as a countertop/coffee tabletop sort of device, or is it due to Alexa, the engagingly sleek voice-driven virtual assistant technology that lives in the Echo?

Alexa's the real hero here — the one who should have her photo on the wall of the Amazon lunchroom as Salesperson of the Month. Alexa is so good she has inspired imitators and in retrospect now looks like the vanguard of an accelerating virtual assistant movement, as retailers of all types are exploring different ways to use the technology. No wonder it appears that robots are taking over the world.

Of course, if Amazon hadn't committed to Alexa so fully and sought to leverage her capabilities so thoroughly, Alexa and the Echo might be more like marginal curiosities. But Amazon has aggressively pushed special deals and promotions through the devices.

The most interesting bit of data from NPD might be the finding that Echo users do half of their online shopping at Amazon after they get the device. Online retailers that aren't experimenting with some similar type of virtual assistant technology might want to get on that right about now. The Echo and Alexa are stealing more than hearts and minds. They're stealing customers and their wallets, too.