That’s the new take on how the quantitative strategy called risk parity will collapse the financial system, as its multitude of bets start moving as one. Apocalyptic predictions tied to the investment programs are popular -- billionaire hedge fund manager Paul Tudor Jones warned they’ll be “the hammer on the downside” when markets are laid low. Briefly: risk-parity funds operate simultaneously in a bunch of different asset classes, weighting their stakes in each according to volatility. If one category of holdings swings around a lot, like stocks, it gets a smaller slice, while quieter bonds get a bigger one. Diversification...