All good things must come to an end. Even Wall Street isn’t immune to this old adage.

A new study by Swiss financial consultants Wellershoff & Partners concluded that the U.S. stock market is likely to take a tumble of at least 30% at some point in the next five years.

What makes this study any different than any other analyst predicting a big drop—or a big increase—in stocks? There’s some pretty impressive statistical analysis behind this projection.

Since the 1980s, investors have championed the concept of studying long-term moving averages of P/E ratios to correctly value the stock market. P/E, or price/earnings ratios are calculations that use a company’s current stock price divided by recent earnings.

One-year earnings, experts argue, are simply too unpredictable to offer an accurate long-term picture. But when earnings are distributed over a longer period—10 years is the benchmark—an analyst can better forecast future price movements. Last year, American economist Robert Shiller won the Nobel Prize largely due to his work in furthering this idea.

The concept, known in the industry as cyclically-adjusted P/E (CAPE) ratio, found that as of the study’s publication date in late July, the market stands at a CAPE reading of 25.69 (it has since risen to 26.1). Either way, that’s one of the highest levels in recorded history, and 55-57% higher than the average historical reading of 16.55.

Sounds great, right? GuruFocus looked at historical CAPE ratios in six-month increments since 1881. Let’s take a look at times throughout history when the CAPE ratio has risen to the current level:

1.)    January-July 1929 (CAPE Ratio 27.3): This was the first time the ratio climbed above the current marker of 26.1. Unfortunately, any momentum generated by this accomplishment was overshadowed by the events of that October—known as the start of the Great Depression.

2.)    January-July 2000 (CAPE Ratio 43.0): It took more than 65 years for the CAPE to approach those lofty heights again, but it reached 26.7 in early 1997 and continued to climb to an unprecedented 43.0 by early 2000. However, starting in January 2000, the market took what would be ultimately a 40% downturn over the next three years—slicing the CAPE ratio in half.

3.)    January-July 2007 (CAPE Ratio 26.8): It didn’t take long for the ratio to climb back above the 26.1 mark, peaking in mid-2007 at 26.8. What came next? The years 2008 and 2009 are still reviled on Wall Street, as the S&P 500 saw a 56% crash over 17 months.

So here we are again, with extraordinarily high CAPE ratios. But the Swiss economists aren’t fooled, pointing out the high correlation between these figures and impending market crashes. “Thus, at least for the U.S. market, it seems fair that the risk of losing capital is substantial,” read the study.

They say that those who don’t learn history are doomed to repeat it. Hopefully, investors will heed the warning this study offers and get out before it’s too late.

For years, investors have lamented the all-profit nature of the financial industry. Whether or not your investments make money, your advisor charges you a fee. In other words, even if the company loses your money, you owe a fee for their ‘services.’ What other business operates this way?

Recently, investment firms such as TD Ameritrade Inc. and Charles Schwab Corporation decided to change that by offering a full refund of fees to customers whose investments depreciate in value. But no legislation or policy addition led to this change. This was a business decision, not a requirement. So what’s in it for these companies?

Regulators approved a plan under which TD Ameritrade investors would receive their money back on all applicable fees in their Amerivest-managed accounts—between 0.3% and 1.25% annually—if those accounts posted negative returns for two consecutive quarters.

“It’s a program by which we hope more people will try Amerivest if we remove one level of doubt or concern,” said spokesman Joseph A. Giannone.

On the surface, it’s brilliant—entice consumers by offering a layer of protection against losses. But let’s look a little closer. The stipulation of two consecutive losing quarters means you’re looking at a period of six months. While fees certainly take a chunk of any account, if you lose 10-15% over any six-month period, how much reassurance does a 1% reimbursement of fees offer?

Dig a little deeper and you’ll find that nothing is guaranteed. TD Ameritrade’s competitor, Charles Schwab Corporation, unveiled a program late in 2013 aimed at ‘guaranteeing accountability’ that allowed some clients to request a refund “if, for any reason, they are not happy.” As of last week, Schwab reported receiving 550 requests for refunds—less than 1% of all eligible accounts. Either they have VERY satisfied customers, or savvy consumers have deduced that the rebate request is futile. (No information was available on how many of the requested refunds were actually fulfilled.)

Lastly, many industry followers are calling into question the consistency of rules and regulations enforcement on Capitol Hill. Many fear that advisors will pull out all the stops to avoid those consecutive losing quarters that would trigger a potential refund. This means adjusting your portfolio, which leads to greater—and more frequent—transaction fees. But as long as the ‘new’ investment doesn’t lose money, the advisor’s upheld his end of this deal. (Notice there’s no promise or even implication of making money.)

Before you run out to Wall Street and create an account that you’ve been told is ‘guarded’ against losses, consider this: these institutions have thrived for years in an environment that offers them—not you—guarantees. Regardless of performance, they’re guaranteed a percentage of your account each year. Why would brokerages voluntarily sacrifice this perk?

What’s the worst month for the stock market historically?

Most people (including myself) probably would’ve guessed October. For example, I knew the Great Depression was highlighted by a late-October tumble in stock prices back in 1929. I know that “Black Monday” occurred in October of 1987. And I remember October as the month when the 2008 downturn went from ‘concerning’ to ‘oh wow, this is serious.’

So it was surprising to find a site that tracks S&P performance since 1950, proving that October is actually a net-positive month for the market. That’s the good news.

The bad news? Its’ immediate predecessor, September, is historically the worst month for stocks. Since 1929, the Dow Jones Industrial Average (DJIA) and S&P 500 have each dropped an average of -1.1% in September.

Why? Different analysts have offered several explanations—draw your own conclusions:

Return to Work. The third quarter of the year begins with July and August, the time of year when most American families (and traders) take their vacation, declining trading volume and making it much more difficult to forecast impending economic events. Cautious investors return to work and sell off stocks, preferring to take a ‘wait-and-see’ approach.

End of Fiscal Year. Many mutual funds see their fiscal years draw to a close on September 30, leading to a sell-off of underperforming securities just in time to file that final report.

Mood/Attitude of Investors. The weather turns cooler, kids are back in school, days are growing shorter. September is the end of summer, typically seen as the light-hearted, relaxed time of year.

“There is this kind of negative vibe out there that tends to accentuate any negative events,” Dan Seiver, a finance professor at San Diego University, said to the Associated Press.

Whether you buy these explanations or not, the September phenomenon has been known for some time—in 2011, Mark Hulbert of MarketWatch pointed out that research has been ongoing for years about this trend. Once such a pattern is known and widely recognized, Hulbert argued, investors find ways to exploit it and eventually reverse the trend. But since such studies began, the gap between September’s performance and that of other months has actually widened.

Lastly, the trend has been remarkably consistent. In each of the nine decades examined, September’s cumulative performance has never ranked higher than 9^th among the twelve months of the year. And it’s been dead last in five out of those nine decades.

So enjoy the last weeks of summer—and the current growth in stocks. But when the calendar changes, maybe your portfolio should follow suit.

For weeks, so-called experts have battled back and forth over whether the stock market will continue to reach new highs, or if it will come crashing down in the next few months. Now, one of the world’s most respected investors has decided to put in his two cents—only in this case, it’s his two billion dollars.

George Soros has spent a lifetime as a trader and analyst. His Quantum Fund is widely recognized as the most successful hedge fund in history. In the 1990s he earned the moniker “the man who broke the Bank of England” when he short-sold the equivalent of $10 billion in pounds. In May 2008, his book The New Paradigm for Financial Markets spoke of a ‘super-bubble’ that would soon burst. The stock market collapse dominated headlines later that same year.

When George Soros talks, the financial world listens.

This time, Soros is putting a significant chunk of money where his mouth is. His most recent 13-F filing (a form required by the SEC of any institutional investment manager with discretion over $100 million or more in securities) showed an increase of over 600% in Soros’ short position against the S&P 500. His total position rose to $2.2 billion, or 17% of his vast portfolio.

A short position occurs when Investor A borrows shares from a broker and sells them on the open market to Investor B. The borrowed stock must eventually be re-purchased (by A) and returned to the broker. If the stock falls in price in the interim, Investor A buys back the stock (from B) at a lower price than he sold it, thus turning a profit. In simple terms, Investor A is betting that the stock’s price will fall, whereas Investor B expects the price to rise.

But Soros hasn’t sold an individual stock—he placed an option on an S&P 500 exchange-traded fund (ETF). He’s betting that the collective stock values of the 500 large companies that comprise that index will take a tumble in the near future. This approach allows him to sell his options—all 11.3 million of them—at a profit, should the market fall.

Investors pay close attention to these 13-F filings—which occur quarterly—to see where the ‘smart money’ is heading. Historically, George Soros has been at the head of the class. Who’s willing to bet against his $2.2 billion?

Many Wall Street experts have spent the summer calling for a market correction. Some call for a 5-10% reduction, while others such as Marc Faber have called for a 20-30% crash.

The truth is that no one knows when the next market correction or crash will happen, nor do they know how significant it will be. But history tells us that it will happen one way or another.

According to Business Insider, corrections (defined as a drop in a particular index such as the S&P 500 of 10% or greater) occur once every 1.5 years, or every 357 trading days. It’s been just about twice as long since the last such event in this market. The most recent correction occurred in the summer of 2011 in the wake of uncertainty in European markets as well as the downgrading of the United States’ credit rating.

Extended correction-free periods aren’t unheard of—but that may be the most worrisome factor of all. Beginning in April 2003, the market experienced no corrections for a whopping 54 months, building up to a then-all-time high on October 9, 2007. Thirteen months later, the S&P 500 was slashed in half by the 2008 crash.

So how will investors know when the correction is beginning? That’s a hard question to answer. The past couple months have been filled with what appeared to be indications of a downward trend, including geopolitical tensions in Ukraine and the Middle East, plus a full 2% drop of the S&P 500 in one day (July 31).

A common means of identifying an impending correction is by setting a support level. Support levels are loosely defined as a number that stocks or index values are unlikely to fall below. If a security or index falls to this level, it’s seen as a test. If buyers begin purchasing the stock at this level, then it’s been supported. If there’s no change in buyers—or worse, a continued selloff—the stock has lost support.

These support level numbers are typically taken from “moving averages”—the mean number at which an index has closed over a set time period of 100 or 200 days.

Of course, it’s difficult to target a precise number as a breaking point for a moving average since by definition, the figure changes daily. But in a bull market, the average is steadily increasing—as is the case right now. Regardless, one school of thought holds that if prices fall below their 200-day moving average, it signifies a reversal of an upward trend in the market—in other words, a correction.

Right now, the S&P 500 is 70-80 points higher than its’ 200-day moving average—but as the average creeps higher, it will be interesting to see whether prices will support that figure. When they don’t, it can be the surest sign of an imminent correction.