OPEC appears to have persuaded investors that it’s making good on promised production cuts. Money managers are the most optimistic on West Texas Intermediate oil prices in at least a decade as the Organization of Petroleum Exporting Countries and other producers reduce crude output. Saudi Arabia has said more than 80 percent of the targeted reduction of 1.8 million barrels a day has been implemented. Oil shipments from OPEC are plunging this month, according to tanker-tracker Petro-Logistics SA . “All the signs are pointing to a pretty significant OPEC cut,” Mike Wittner, head of commodities research at Societe Generale SA in New York, said by telephone. “Until this week we were only getting data from the producers, now the tanker traffic seems to be supporting this view.” OPEC will reduce supply by 900,000 barrels a day in January, the first month of the accord’s implementation, said the Geneva-based Petro-Logistics. […]