Calculating the reward-to-variability ratio, introduced by William Sharpe in 1966, of Facebook and Amazon stocks in 2016. S&P 500 data as benchmark.

1. Daily stock returns: % change in value from one day to next ( stock_returns and sp_returns)
2. Compare Facebook and Amazon's respective difference in daily returns w.r.t. those of S&P 500, namely excess_returns
3. Calculate average and std of Facebook and Amazon's excess_returns
4. daily_sharpe_ratio = avg_excess_return.div(sd_excess_return), annualize by sqrt(252), 252 being the number of tradings days
5. Amazon's Sharpe Ratio was 2x that of Facebook's due to its higher returns. Cool insight into optimal investment decisions back in 2016.