When it comes to your investment portfolio, what happens if the next 18 years don’t look like the previous 18 years or 36 years? Are you financially prepared for a generation where returns are very low? I believe most Americans are not. They simply haven’t saved enough, and the passive investment strategy that most people use to invest — buying market capitalization-weighted indexes — may not be the best place to be in a world where the future increasingly looks very different from…