The S&P 500 goes up in some years and down in others. Historically, the odds of a positive return in any given year have been about 75%. But the probability improves as the time horizon lengthens. Indeed, the S&P 500 returned 12.6% annually over the last decade, and investors can expect similar results (plus or minus a few points) over the next decade. In short, history says the stock market will soar in the long run, which means investors can always find buying opportunities. Currently, Uber Technologies ( ...