http://www.computerworld.com/article/2924322/apple-mac/by-the-numbers-apple-iphone-ipad-and-mac-quarterly-sales.html
Apple iPad sales have been somewhat flat the past couple of years, a trend that our own Gregg Keizer reported on recently. But how flat is demand? And is the number of iPads sold actually starting to trend down? Sales of iPads – as well as iPhones and Macs, actually – are cyclical, with many more sold close to Christmas than are in mid-spring. That makes it hard to look at raw quarterly numbers and see a trend. But, as blogger Dr. Drang posted with accompanying graphics, if you calculate a 4-quarter moving average (use the average of the most recent 4 quarters as each data point instead of the stand-alone quarterly number), you'll get a much more useful picture of what sales are doing.
Using data from Bare Figures, here's what moving averages look like for iPad, iPhone and Mac unit sales. While overall revenue lets you know how important various product lines are for a company, unit sales can be a better measure of waxing and waning popularity.
On the graph below, you can click (or tap on mobile) on device names in the legend to turn them on and off – you'll need to turn off iPad and iPhone data in order to see the trend for Macs, since unit sales are so much lower. Mouse over (or tap on mobile) points to see underlying data.
2015 Q1 iPhone- 52.5 million units sold
2015 Q1 iPad-14.9 million
2015 Q1 Mac- 5 million