Apple iOS hit the market in 2007 and was quickly joined by Android phones near the end of 2008. In the Fourth quarter of 2008, iOS had 10.5% while Android had an initial share of only 1.5%. Since, 2008, Android has steadily outpaced Apple and in 2015, Q4 Android had 80.7% of the market while Apple had 17.7% of the worldwide smartphone market.
The above and below figures show worldwide smartphone sales by quarter. The data were taken from here.
Data represented as area.