Why the Five-Year Anniversary of the Stock Market Crash This Week Has Investors Worried

The stock market crash this week that occurred five years ago this Sunday marks a solemn anniversary for U.S. stock markets.

Subprime financial crisis-related events would ultimately become responsible for five out of the top ten biggest single-day Dow Jones Industrial Average stock market crashes, including the top two spots.

After the Dow Jones hit an (at the time) all-time high on Oct. 9, 2007, at 14,164.43, it would fall by more than 50% to 6,594.44 by March 5, 2009 – a little under 18 months later.

U.S. markets hit their lowest point in the crash on March 9, 2009; the 5-year anniversary of that low point is this Sunday.

Since that day, U.S. markets have skyrocketed. The S&P 500 Index is up 174.7% (1,193.85 points), the Dow Jones Industrial Average has posted a 148.35% gain (9,830.98 points), and the Nasdaq is up 235% (3,040.5).

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In fact, as of this week, the bull market – defined as a period in which the S&P 500 gains 20% or more – ranks as the sixth longest since 1928, according to Bespoke Investment Group research.

However, the longer this rally lasts, the greater the anxiety there will be a stock market crash, or at least an official stock market correction – defined as a decline of 10% or more.

"I am very concerned about a correction right now," Money Morning Chief Financial Strategist Keith Fitz-Gerald said on Friday. "The past few weeks have seen higher prices and lower volume. This is like climbing a mountain into thin air – every step higher gets harder. Sooner or later, the markets are going to have to take a breather and turn around."

Here are the three signs that have investors worried we're due for a stock market crash or correction soon…