New York–based Davidson Kempner Capital Management remains the 18th-largest hedge fund in the world for the fourth consecutive year. Though its ranking didn't change from 2014, the multistrategy hedge fund firm boosted capital by more than $2.8 billion by the end of the year, thanks to well-performing funds and a 2 percent management fee. Co-founder Thomas Kempner Jr. earned $150 million in 2012, placing No. 36 on Alpha's Rich List, thanks to the growth and performance of his firm. Kempner, a former Goldman Sachs bond trader, specializes in risk arbitrage, and his firm invests primarily in bankrupt companies. Outside of work he is…