Thanks to the numerous exchange-traded funds (ETFs) that are available on the market these days, investors can easily add exposure to their portfolios to whatever themes or sectors they are bullish on. However, sometimes it's best to keep things as simple as possible.

For example, allocating capital to an investment vehicle that tracks the S&P 500, such as the SPDR S&P 500 ETF Trust (SPY 0.44%), is a very prudent decision. The numbers speak for themselves.

Had you invested $1,000 in this ETF in early October 2020, here's how much you'd have today.

The letters ETF superimposed over stock charts tickers.

Image source: Getty Images.

Better than a double

Over the trailing five-year period, the SPDR S&P 500 ETF Trust has generated a total return of 113% (as of Oct. 2), which would have turned $1,000 into over $2,130 today. It's really difficult to complain about any investment that more than doubles your initial capital over a 60-month stretch.

Even though this has been a volatile year, this ETF has put up a double-digit gain. It now trades in record territory.

It's a good idea to be optimistic

Observers continue to worry about the market's valuation these days. However, it's still worth considering investing in the SPDR S&P 500 ETF Trust right now. Over long periods of time, those investors who are able to put money to work early and often benefit from having time on their side. And that's a powerful force that can lead to a fantastic outcome.