Weak signal given the size of the companies and their volatilities.<p>Let's observe the quoted, albeit stale, Google market capitalisation of $249.2 billion with a current vega-weighted mean implied volatility (market's opinion of what Google's volatility will be) of 31.12% and the quoted Microsoft market cap of $248.7 billion with an IV index of 22.51%. The question is, assuming these two Gaussian random variables vary independently [1], what is the probability that GOOG is still bigger than MSFT in one year? The answer is a <i>hair</i> above 50%. Plugging in $249.65 billion for Google and $248.02 billion for Microsoft (closer to present values) this probability rises closer to 51%.<p>Conclusion: insufficient evidence that this is more than random market jittering just yet.<p>[1] If this were more than a quick, stylised analysis I'd construct a covariance matrix or copula to describe the dependency structure. Given the razor thin odds, however, it is unlikely that correlation will help the OP's case too much.