MarketWatch Premium: Good news could be bad news: Stock market bullishness has reached an extreme

The stock market has had relentless gains this week. Look for it to struggle over the next couple of weeks.

That’s because stock market timers rarely have been as bullish as they are today. As contrarian analysis teaches us, the market faces stiff headwinds when there is as much bullish exuberance as prevails today.

One measure of this exuberance…