Better Buy: Vanguard High Dividend Yield ETF vs. SPDR S&P Dividend ETF

Exchange-traded funds (ETFs) are a wonderful investment option for many investors -- but only if you truly understand what you're buying. And if you're looking for an ETF that pays a high dividend yield, you can't simply pick one with the word "dividend" in its name. Vanguard High Dividend Yield ETF (NYSEMKT: VYM) and SPDR S&P; Dividend ETF (NYSEMKT: SDY), for instance, have far different methods and goals, though they may sound similar.

Here's what you need to know before making a choice between Vanguard High Dividend Yield ETF and SPDR S&P Dividend ETF.

Only high yields need apply

Vanguard High Dividend Yield ETF is designed to track the performance of the FTSE High Dividend Yield Index. It is passively managed, aiming to mirror the index perfectly. The only caveat here is that the index excludes real estate investment trusts, so it doesn't actually track the entire spectrum of dividend-paying companies. According to Vanguard's website, the ETF "provides a convenient way to track the performance of stocks that are forecasted to have above-average dividend yields."

If you're looking for a way to invest in a portfolio of high-yield stocks, this would seem like an ideal option. The yield is around 2.8%, which is notably higher than what an S&P 500 index fund would provide (around 1.8%).

The word yield spelled out using dice sitting atop stacks of coins
The word yield spelled out using dice sitting atop stacks of coins

Image source: Getty Images

That sounds great on the surface, but there are some unanswered questions. For example, is yield the only criterion for inclusion in the index the ETF tracks? How are the weightings of the index components determined? These are important questions that seem to go unanswered on Vanguard's website and in the fund's prospectus and annual report.

Vanguard High Dividend Yield ETF is built off of an FTSE index -- but it's not clear which one. The ETF's holdings appear to be a subset of the FTSE All-World Dividend Index, which is in turn a subset of the FTSE All-World Index. I couldn't find a specific index to research, but at the end of the day, it appears the index on which Vanguard High Dividend Yield ETF is built ranks U.S. stocks by forward yield, selecting the top 50% of the group for the index, which is then weighted by market cap. It gets rebalanced twice a year.

There's a simple logic to the approach of using dividend yield in this way. In effect, it will lead you to invest in great companies that have historically paid generous dividends, as well as out-of-favor companies that have high yields because their stock prices are depressed.