Historical Bitcoin returns vs Altcoins

In my pursuit to analyse Altcoin returns if you had bought the entire market like an index fund, I just ran some numbers:

Period Bitcoins Altcoins
Sep 2013-2016 470% 1970%
Sep 2015-2016 170% 268%
Sep 2014-2015 -47% 20%
Sep 2013-2014 300% 369%

I’ve yet to work out risk return on altcoins but I suspect the combined volatility of the entire altcoin market will be quite comparable to Bitcoin’s.