Apple can’t grow like this forever. No company can.

In a few short years, Apple has become the biggest company on the planet by market value — so big that it dwarfs every other one on the stock market. It dominates the Standard & Poor’s 500-stock index as no other company has in 30 years.

Apple’s market capitalization — the value of all of the shares of its stock — is more than $758 billion, greater than any other company’s. Yet the Wall Street consensus is that Apple is still having a growth spurt. In fact, if Apple’s watches, phones, laptops and other gadgets and services keep generating favorable publicity — and if its quarterly earnings report on Monday is as strong as the market expects it to be — there’s a reasonable chance that Apple’s value will keep swelling. Not far down the road, it might even reach the $1 trillion level that some hedge funds predict.

But even if Apple still has some room to run, there are some early warning signs. After all, the company has already crossed a significant threshold. In February, it grew to twice the size of the next biggest company in the S.&P. 500, a rare feat of financial dominance, and one that hasn’t happened since Ronald Reagan was president.

I checked the numbers with Howard Silverblatt, senior index analyst at S.&P. Dow Jones Indices. He found that the last market colossus to tower over its competitors by a two-to-one ratio was IBM, which did it in three successive years: 1983, 1984 and 1985. “That was when PCs were new,” he said, “and just about everyone thought IBM would rule the world.”