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,...