Johannesburg - Insurer Santam [JSE:SNT] posted a 16% rise in first-half profit on Wednesday, boosted mainly by the underwriting business but investment income fell as equity markets stayed weak. Santam said headline earnings per share totalled 593 cents in the six months to end-June, compared with 511c in the same period a year earlier. Gross written premiums rose to R8.2bn from the R7.7bn realised a year earlier. However, investment returns fell to R193m from R203m in the comparable period of 2010. Santam expects both underwriting margins and investment portfolio to come under pressure in the second half of the year. The company declared a 200c dividend for its half year, compared with 685c previously, which had included a 500c special dividend. The short-term insurer that is majority held by Sanlam also said that it acquired a 55% stake in Mirabilis Engineering Underwriting Managers in March.