What if the glass is half full? What if the optimists are right?

Although no one can predict the next big move in stocks, and you don't want to bet your retirement portfolio on it, it's not hard to see the case for a bull market in 2020 — even after a spectacular year for stocks in 2019. (Stock prices are up more than 28% with six trading days left in the year.)

With interest rates and inflation lower than expected and no sign of change in these trends on the horizon, the stock market multiple is higher than normal and arguably could easily go higher.