Indexes have changed a lot over the past century. What was once state-of-the-art is now antiquated. The first indexes used information that was available, not what was best for building a portfolio.

The S&P 500 has gotten more expensive because of outsized gains in recent years. The index is much more growth-oriented than in the past, which helps justify a higher valuation. The S&P 500's ...

This single investment can quickly have you well diversified globally -- and collecting a nearly 3% dividend yield.