BMI was designed to indicate the money flow into or out from the market. And it has been a leading indicator for two years. The recent change could signify that we are now in a different phase of the bull market.
In the past two years when BMI was leading, investors have correctly anticipated the trajectory of the market. But from now on, investors' predictive power is likely diminished, and they may just follow the market up and down. Indeed, in the past two years, the macro economic trend is determined by fiscal and monetary stimulus, which is relatively easier to predict. But from now on, with stimulus being unwound, the effect of other factors started to emerge. The market internals are a lot more complicated and it's thus harder for investors to predict.
I'll keep an eye on this. If there is any negative divergence down the road, I'd like to favor the chance that BMI will follow S&P 500. Still a negative divergence would mark a significant bottom or top of the market.