March 4 (Reuters) - U.S. property data and analytics company CoreLogic Inc rebuffed peer CoStar Group Inc’s sweetened buyout offer, saying it required improvement in terms of value. Earlier this week, CoStar raised its offer to buy CoreLogic by adding another $450 million to its original $6.9 billion all-stock proposal, hoping to seal a deal and triumph over another competing bid by private equity firms. Under the new proposal, CoreLogic shareholders would receive $6 per share in cash and 0.1019 shares of CoStar’s common stock in exchange for each share of CoreLogic, totaling $90 per share. “$6 per share in cash does not meaningfully reduce CoreLogic shareholders’ exposure to the concerning volatility of your stock,” CoreLogic said in a letter addressed to CoStar on Thursday, adding the revised proposal represented a significantly lower implied total per share value than its previous offer. Despite CoStar sweetening its bid by adding some cash on Monday, the primarily stock offer was still worth less than when it was unveiled on Feb. 16, because of the decline in its shares. CoreLogic also said the $6 billion offer by private-equity firms Stone Point Capital and Insight Partners announced last month remained in full force.