Yes, there is, there's lots of math around this. Nobody listens to it (other than some of the extremely large pension investment firms, which in fact DO follow the math). Because rather than a dry technical mix of investments, doing things like 'buy silver because it's better than gold' sounds so much better. Or get in on Apple. Or whatever. All these ideas have been shown to less than optimal strategies, but there's no emotional fun or commission in them, so nobody sells them and nobody buys them. And the other problem is, strategies are only higher yield and lower risk over the long term. So as soon as things get tough, people bail. Most folks can't see that to get a long term 6%, you're going to get 8% some years (not the 12$ others are getting) and you're going to eat 2% some years (but not get the -15% others are getting). When you're earning 8% and everyone around you is earning 12%,it's natural to want to jump ship.
There are investments that are inversely correlated, and others that are not correlated. The right mix means that when something drops, part of your investments drop - but other parts will rise, and other parts are unaffected.