If you've been an investor for more than a few months, you've almost certainly heard the adage "the trend is your friend." This bit of wisdom has been proven correct so often that it has assumed a place as a universally accepted stock market "rule." Most of us think of trends as market momentum - a shorter-term manifestation that lasts from a few hours to a few weeks. But there's another kind of trend - one that's both longstanding and quite powerful - that can deliver hefty profits to those who understand its value. Investors interested in long-term investing strategies can take a close look at global demographic trends.