2019 was the year one of the longest bull markets on record was supposed to come to an end — “Everyone says so.”

Instead, by Dec. 1, the market had gained well over 20%, or about twice its yearly average. How could so many knowledgeable market watchers have been so wrong?

What We Know — and What We Don’t

Perhaps the most basic truism about the stock market is that it’s cyclical — first it goes up, then it comes back down, sometimes landing relatively softly and at other times with a loud crash, wiping out trillions of dollars of investor wealth.

But then the cycle repeats, and repeats again — as it has, predictably, for over a hundred years. Market watchers also know how long, on average, this cycle takes. The upward part, the bull market phase, averages over four years; the downswing, the bear market phase, about 14 months.

But while the cyclical nature of the market is well-known, as are the average lengths of its bull and bear market components, what we don’t know is how long a given bull or bear market will last. And they vary greatly in both length and magnitude.

Since the 1930s, three bull markets have lasted over 10 years and two more have lasted less than four. Similarly, bear markets have lasted for as little as three months or for over two years.

Trying to use average lengths to predict when the current bull market will likely end is a little like having two children, one a school linebacker, the other a ballerina, and buying their clothes based on their average height and weight.

If you’re trying to figure out what’s going to happen next in the stock market, market averages are simply not useful information. Which doesn’t keep market pundits from trying.

A Very Brief History of Market Predictions

The variability — and unpredictability — of bull and bear market lengths only hint at the complexity and quantity of market information available to anyone who chooses to use it to predict the market’s future.

Here are a few amusing quotes that give you the general idea of the usefulness of all this data. The quotes below appeared in respectable market analyses at some point prior to the beginning of 2019:

The Butterfly in Brazil vs. the Hurricane in Texas

Just for the record, in 2019 interest rates fell (which has also led to another pessimistic prediction of economic gloom). The reality is that there are so many variables that affect large scale entities like financial markets that almost any collection of data will be so incomplete as to be an inadequate basis for assessing what will happen next.

Nevertheless, self-appointed experts keep trying to tell you what will happen in the market next. As to how well they can do that in reality, there’s an abundance of serious data available indicating that they generally fail.

But I’ll just give you this: In 2017, one of the British newspapers conducted a yearlong experiment matching the results of stock-picking professionals with a pet cat (named Orlando). You guessed it, the cat won, using the highly efficient TTMSP method — throw a toy mouse at a stock page. Similarly, superior results have been obtained by a chimp throwing darts.

The unpredicted and unpredictable ways in which so many variables can determine what happens next in large-scale systems has given rise to the “butterfly in Brazil” assessment, where something as inconsequential as the flap of a butterfly’s wings in Brazil can sooner or later produce a hurricane in Texas.

As it turns out, even that is probably wrong. If a butterfly caused it, we’d have no way of knowing — there’s just too much relevant data to sort through even for today’s supercomputers.

What I can tell you, based on my 10 years’ experience as a stock market professional, is this: when a broker or a media pundit tells you what will happen next in the stock market, or even where it’s trending, pay as little attention as possible. Alternatively, consult Orlando the cat.