A Bullish ETF Trader With $6 Billion Just Made Some Risky Bets

One big investor flipped the risk-on switch this week, trading about $6 billion worth of exchange-traded funds as global markets flashed bullish signals following a brutal December.

On Wednesday, a frenzy of fresh trading hit U.S-listed products, and was likely the work of a single manager, according to Josh Lukeman, head of ETF market making for the Americas at Credit Suisse Group AG. Among the moves: yanking cash from investment grade bonds and splashing it into high yield, and swapping out developed-market equities for EM.