Bull market. Bear market. Everyone drops these terms like the meaning is obvious. Most people can't actually define either one.
A bull market is a 20% climb from a low. A bear market is a 20% collapse from a high. That's the whole definition. No vibes, no feelings, just a number.
The S&P 500 has flipped between the two roughly every few years since the 1920s. Get the cycle wrong and you'll make exactly the wrong move at exactly the wrong time. Start with the bull side, since that's the one everyone thinks they already understand.
What actually defines a bull market
A bull market is a sustained rise of 20% or more in a broad index, measured from its most recent closing low. For U.S. stocks, that benchmark is almost always the S&P 500. The rise has to hold, not just spike for a week on a good jobs report.
Bull markets tend to show up when the economy is expanding. Corporate earnings grow, unemployment is low, and investors keep buying because the recent past has trained them to expect more upside. That optimism is self-reinforcing until it isn't.
How long does that actually last? Market history says anywhere from four to 11 years, based on S&P Dow Jones Indices data going back nearly a century. There's no fixed lifespan. Bull markets don't die of old age, they die of a specific trigger, and that trigger is exactly what flips the market into its opposite.
What actually defines a bear market
A bear market is the mirror image. The index closes at least 20% below its most recent high, and the decline sticks around instead of bouncing back in a week. Sentiment flips from confident to defensive almost overnight.
Bear markets are shorter than bull markets on average, but they hit faster and hurt more per month. The 2020 COVID crash wiped 34% off the S&P 500 in about a month, then fully recovered in under five months. That is the exception, not the rule.
What actually causes one? Usually a mix of tightening interest rates, a slowing economy, or a shock nobody priced in. Rising volatility is often the earliest tell, well before the 20% threshold is officially crossed. That's the part worth remembering before you look at any chart.
Definitions are one thing. Spotting the cycle while you're actually living through it is harder. Here's what to actually watch.
How to tell which cycle stocks are in right now
You don't need a Bloomberg terminal to figure out where you stand. Two signal groups do most of the work: price action and sentiment. Look at both before you act on either one alone.
Price action and moving averages
Watch whether the index is making higher highs and higher lows, or the reverse. A widely used technical marker is the 200-day moving average. Index prices holding above it for months signal a bull phase. Prices stuck below it, with the average itself sloping down, signal a bear phase.
Breadth matters as much as the headline number. A market where only five mega-cap stocks are pushing the index higher while most stocks lag is a weaker bull market than one where gains are broad. Watch the percentage of stocks trading above their own 200-day average, not just the index.
Investor sentiment and volatility spikes
Price isn't the only tell. Sentiment tends to lead it. A spike in trading volume on down days, a jump in the VIX, or a sudden shift in market sentiment surveys from greed to fear often shows up before the 20% threshold is officially hit.
None of these signals work in isolation, and none of them predict the exact top or bottom. They tell you which regime you're probably in right now, which is a different and more useful question than guessing where the market goes next. And knowing the regime is only half the job. What you do with that information matters more.
What to actually do differently in each market
The instinct in a bear market is to sell everything and wait for calmer water. That instinct usually costs you the recovery, because the biggest up days in market history cluster right around the worst down days.
This chart makes the cost concrete. Two investors, same starting money, one stays fully invested and one tries to dodge the rough stretches.
In a bull market, the risk runs the other way. Chasing every rally with fresh cash, without checking whether your allocation still matches your actual risk tolerance, sets you up for a harder landing when the cycle turns. This is exactly why diversification matters more when things are going well, not less.
A weakening economy that hasn't yet triggered a full bear market is often called a recession warning sign, and it's worth treating seriously before the 20% threshold confirms it. If you're still deciding whether now is the right moment to put new money to work, our piece on whether you should invest now walks through that decision directly. And if you're newer to this, our rundown of 5 investing mistakes every beginner should avoid covers the panic-sell trap in more detail.
Reading the cycle beats guessing the bottom
Nobody rings a bell when a bull market ends or a bear market bottoms. That's the uncomfortable truth behind every headline that claims otherwise.
But you don't need perfect timing to make better decisions. You need to know which regime you're in, watch the same signals every time, and adjust your behavior instead of your predictions. The market has recently been volatile enough that some readers may recognize the pattern from our earlier look at why this selloff felt different. The mechanics behind bull and bear markets don't change. Only the headlines do.
If you want to check where individual stocks actually stand right now instead of guessing from the index alone, run them through the Stoxcraft screener. It's a faster way to see which names are holding up and which ones are quietly already in their own bear market.
