Hedge funds posted a loss of 5.7 percent last year as managers struggled to capitalize on volatility and were roiled by political uncertainty. For December, funds lost 1.9 percent, according to preliminary figures from the Bloomberg Hedge Fund Database. The industry suffered through one of its worst years in 2018. Many managers not only failed to make money but did worse than the broader market. The return of volatility posed a challenge. The prospect of a trade war with China and the combative stance of President Donald Trump didn’t help.