The data is shared by the NPD Group and collected using NPD's Checkout service, which tracks and analyzes consumer purchases by multiple offline retailers.
According to the data, HomePod is second only to Amazon Echo Dot as the smart speaker with the second best selling volume.
Although it is reported that only HomePod sales data more than other smart speakers, but NPD Group did not give the exact number of sales.
By convention, Apple generally does not disclose its sales data, but we may be able to get the answer from Apple's next phone earnings, the general Apple will be in the earnings report will be classified as 'other' HomePod other categories include Apple TV, Apple Watch, AirPods, iPod, Beats and other Apple branded and third-party accessories, etc. It is clear that it will also include HomePod.
Loop Ventures analyst Gene Munster predicts that HomePod will hold 12% of the world's smart speakers by 2018 and is expected to sell 7 million units.