According to data from analytics firm Localytics (via Forbes), it seems that Apple is selling over a combined 1 million units of the iPhone 8 and iPhone X on a daily basis. According to the numbers, the iPhone 8 represents about 2.22% of total iPhones in the market and translates to about 17.5 million sold.
The iPhone 8 Plus appears to be the more popular of the two and represents 2.94% of the iPhone market and is about 23.2 million sold. As for the iPhone X and given that it was released later, it is said to account for 2.63% of the market and represents about 20.7 million units sold. Note that these aren’t official figures so do take it with a grain of salt for now.
This seems to be in line with a report from Mixpanel last week which revealed that towards the end of November, the iPhone X managed to catch up with the iPhone 8 and 8 Plus in terms of adoption, and outpaced them in December.