Elon was not talking about year over year growth, he was talking about doubling fleet size.
2012: 2,500
2013: 24,500
2014: 57,500
2015: 107,500
They have guided for 1600-1800/week for 2016, so over 80k, approximately doubling fleet size once again.
First of all, let's get the numbers right:
Tesla Model S annual totals:
2012: 2,650
2013: 22,477
2014: 31,655
2015: 50,366 (This annual total is not 100% accurate)
Tesla Model S cumulative annual totals:
2012: 2,650
2013: 25,127
2014: 56,782
2015: 107,148 (That's NOT including those 214 deliveries of Tesla Model X in 2015)
Growth of the cumulative Tesla Model S fleet in 2013 was extremely high (almost 9 times 2,650).
Growth of the cumulative Tesla Model S fleet in 2014 was 125.98 %.
Growth of the cumulative Tesla Model S fleet in 2015 was 88.7 %.
Growth of the cumulative Tesla Model S fleet in 2016 will most likely be even lower than 50%.
To be really accuarate we have to do:
+ 214 deliveries of Tesla Model X in 2015
+ 2,500 Tesla Roadsters (2008 - 2012)
Tesla Fleet annual totals:
2012: 5,150 (That's 2,650 Tesla Model S + 2,500 Tesla Roadster)
2013: 22,477
2014: 31,655
2015: 50,580 (This annual total is not 100% accurate)
Tesla Fleet cumulative annual totals:
2012: 5,150
2013: 27,627
2014: 59,282
2015: 109,862 (That's including those 214 deliveries of Tesla Model X in 2015)
Growth of the cumulative Tesla Fleet in 2013 was extremely high (436.45 %).
Growth of the cumulative Tesla Fleet in 2014 was 114.58 %.
Growth of the cumulative Tesla Fleet in 2015 was 85.32 %.
Growth of the cumulative Tesla Fleet in 2016 will most likely be lower than 80%.