(Bloomberg) -- Ray Dalio’s Bridgewater Associates and Jim Simons’ Renaissance Technologies beat their rivals in a tough year for hedge funds in 2018, making a combined $13 billion for their investors. The profits accounted for more than half the money generated by the top 20 managers last year, according to estimates by LCH Investments NV, a fund of hedge funds. Firms outside that top group lost more than $64 billion as stock declines and volatility took their toll.