The way the stock market has performed over the past few months, your retirement account is probably going down, not up. But keep in mind that the average length of a bear market is roughly nine months, while the average length of a bull market is about 2.7 years. Also, according to research from Hartford Funds, stocks lose 36% on average in a bear market and gain 114% on average during a bull market.

Over the long term, the bulls usually win out as the average annual return for the S&P 500 over time is roughly 10%. But even still, if you want to retire a millionaire, you can't rely on your retirement account or 401(k) alone. According to a recent study by Vanguard, the average American has just $225,000 in their 401(k) plan at age 65. So, to get to that $1 million by retirement, it is going to take some additional investments. A good option to supplement your 401(k) plan are exchange traded-funds (ETFs), which are diversified baskets of stocks.

A parent and an advisor counseling a son on retirement and saving.

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Invesco S&P 500 Pure Value ETF

There are thousands of ETFs to choose from, and the vast majority of them track an index or benchmark. Some may be broad and hold thousands of stocks of various market caps, industries, and investment styles, while others may be more narrowly focused on a particular sector or style.

As most segments of the market are either in bear market territory -- defined as a decline of 20% -- or near it, many excellent ETFs are available at a lower price point. But if you are looking for a fund that outperform the market now and generate steady long-term returns in the future, consider the Invesco S&P 500 Pure Value ETF (RPV 0.37%)

This ETF invests in value stocks within the S&P 500, tracking the S&P 500 Pure Value Index. The index includes stocks that have the highest value score based on three metrics: book-value-to-price ratio, earnings-to-price ratio, and sales-to-price ratio. It is designed to weed out everything but those considered deep or pure value stocks -- meaning there are no blends in this portfolio. And the stocks with the highest value scores get proportionally greater weights in the portfolio.

Currently, the ETF holds about 122 stocks with Berkshire Hathaway as the largest holding. Marathon Petroleum is the second-largest position, while insurance company Cigna is third. The largest sectors are financials (30%), healthcare (12%), energy (10.5%), and consumer staples (10%).

Returns that are beating the market

The ETF is up about 2% year to date, which is far better than the S&P 500, which is down 17% as of May 25. It is also better than the S&P 500 Value Index, which is down about 5% year to date.

But letʻs look at the longer-term returns. The ETF has been around since 2006, so it has a track record to lean on. Over the past 10 years it has posted an annualized return of about 13%, which is roughly on par with the S&P 500 over that time. Since its inception in 2006, it posted an annualized return of roughly 9% as of May 25, and if you go back 20 years, the index it tracks has returned roughly 10% annually.

Over the next few years, this ETF may well outperform the S&P 500 as value typically outperforms growth during recessionary periods and coming out of recessions. But even if the economy doesn't go into recession, value typically does better than growth in a period of rising interest rates, and we are in that type of environment now and for the foreseeable future.

However, over the longer term, know that this ETF will lag behind growth ETFs during bull markets. But it still should generate steady returns and act as a nice hedge against the broader market during downturns.

Making a million?

So back to the question of how this ETF can help you reach your retirement goals. If you're the average American, according to the Vanguard survey, you'll need another $750,000 to reach $1 million. But if you are a Motley Fool reader, you are obviously above average, if I don't say so myself, and interested in investing. As such, let's say you started early and are on pace to have $500,000 at age 65 when you retire -- you'd need another $500,000 to reach $1 million.

You could get pretty close if you invested in this ETF early enough. For example, if you put $5,000 into the Invesco S&P 500 Pure Value ETF at age 30, with 35 years until retirement, investing $100 per month, and generating an average annual return of 10%, you'd have roughly $546,000 by age 65.

The key, of course, is starting early. Even if you don't have 35 years -- say you only have 20 years until retirement -- the sooner you start the better off you'll be.