EMC Insurance Group Inc.’s proposal to take the company private now has the backing of two independent proxy advisory firms, the Des Moines-based insurer announced. Last week, a leading independent proxy advisory firm, Glass Lewis & Co., joined another independent proxy advisory firm, Institutional Shareholder Services, in recommending that EMCI shareholders vote in favor of Employers Mutual Casualty Co.’s proposed acquisition of all of the shares of EMCI that EMCC does not already own. The recommendations align with the advice of EMCI’s board, which recommends approval of the proxy statement that was filed with the U.S. Securities and Exchange Commission last month. Shareholders who fail to vote or file an abstention will have the same effect as a vote against the transaction. As previously announced, the vote will take place at a special shareholders meeting on Sept. 18 at EMC’s downtown Des Moines headquarters.