Brokerage SG said on Friday it had reduced its rating on Lafarge , the world’s largest cement producer, to "sell" from "hold", partly due to rising costs at the company. SG also cut its fair value target on the stock to Euro 63 from Euro 80. On Thursday, Lafarge shares fell to an 18-month low after it raised doubts over whether it could meet an already-lowered profit forecast. Lafarge shares were down 0.3 per cent at Euro 67.30 earlier today.