Platinum Underwriters Holdings has posted second-quarter profit of $49.9 million compared to net income of $67.5 million in the prior year.The company said results for the quarter include net premiums earned of $142.9 million, net favourable development of $44.1 million, net investment income of $17.8 million and net realised gains on investments of $11.7 million, partially offset by $18.6 million of losses from second quarter major catastrophes."Our performance reflects favourable prior period development, investment losses on a total return basis and active capital management,” Michael D. Price, Platinum's CEO, said.“Our book value per common share was $59.67 as of June 30, 2013, a decrease of 0.9 percent from March 31, 2013."Platinum’s main subsidiaries are in Bermuda and the US.Mr. Price added, "Absent major events in the insurance or capital markets, we expect mild deterioration in overall reinsurance rate adequacy. With our strong balance sheet and experienced underwriting, investment, and risk professionals we are well positioned to operate effectively in the current challenging market conditions."The company’s combined ratio was 74.4 percent, a decrease of 1.9 percentage points..Net premiums written increased $4.9 million, or 3.5 percent, and net premiums earned decreased $2.1 million (or 1.5 percent).Net investment income decreased $8.3 million, or 31.9 percent.For the six months ended June 30, profit was $136.4 million with a combined ratio of 60.7 percent.