Bobby Yip / Reuters

Welcome to what is poised to be—by most counts—the longest bull market on record in the United States.

For roughly 3,453 days the S&P 500 has been on a mostly steady upward trajectory. To many, these prolonged gains are unambiguously good news, particularly when combined with an economy that is strong and stable—which this one is. The market rally has resulted in gains of more than 300 percent and trillions of dollars for investors since the nadir of the Great Recession nine and a half years ago.

How did we get here? There are some who will undoubtedly thank the president. And it’s true that in the wake of the election, the markets enjoyed what was then dubbed the “Trump Bump” as many investors presumed that a corporation-friendly administration would help profits. But this rally started long before Donald Trump’s name was even seriously mentioned in the political arena.

The market started climbing in 2009, right after the country felt the worst losses of the recession. Part of the reason this market run has lasted so long is because the initial recovery from the recession was so slow and the losses were so significant. Those long, plodding years trying to recoup the losses of the Great Recession count toward this bull market, too. The current bull cycle was borne of prolonged quantitative easing, suppressed interest rates, and escalated stock buybacks, among other techniques used by the government and corporations to help markets recover.

This rally has weathered political uncertainty, a surprising presidential election, a pseudo–trade war, a barrage of potentially market-moving tweets, and several sizable drops. Skeptics who have tried to pronounce the death knell of this rally have been proven wrong again and again as the stock market continues to shake off bad news and climb to new highs.

But that won’t always be the case. Those celebrating this historic rally should remember that the sheer duration of a bull market doesn’t guarantee economic health. In fact, some experts worry that the longevity of the market rally is actually cause for concern: If this is the peak, a crash could be on the way. It’s also worth noting that while historic streaks can provide clues to what’s happening in the market more broadly, actual bull and bear markets, and recessions, are determined retroactively, not in the moment. And across the financial sector, analysts can often measure highs, lows, and other market highlights in myriad ways. All of that means that putting this particular moment in context is especially hard while it’s still happening.

For now, most of Wall Street is celebrating: Given the low unemployment rate, some moderate wage growth, and the fact that the economy is expanding, it’s not likely that the country will be plunged into a recession tomorrow. That means that by most accounting, this rally is the most significant since the one that preceded it, when the market rose steadily for most of the 1990s— during the dot-com boom. It’s nearly impossible to say when, but eventually this bull market will end the way most have in the past—with a downturn.

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