OPEC's 10 members with output quotas cut 23,000 barrels per day (bpd) from their production in December to 23.65 million bpd, OPEC said on Friday. In its monthly oil market report, the Organisation of the Petroleum Exporting Countries said December's output was 453,000 bpd above the cartel's self-imposed ceiling of 23.20 million.
Nigeria displayed the weakest adherence to its quota, pumping 200,000 bpd above its 1.91 limit, OPEC found in a survey of secondary sources used to monitor its own output.
Iraq, which is exempt from the quota system because of United Nations sanctions, pumped 2.07 million bpd - 715,000 bpd less than November.
The sharp drop in Iraqi production - the second in two months - was mostly responsible for a 738,000 bpd drop in overall OPEC output to 25.73 million bpd, the report showed.
OPEC implemented its fourth successive quota reduction on January 1, which cut a massive 1.5 million from the 10 countries to set a new limit of 21.70 million bpd.
The report revised lower by 190,000 bpd OPEC's estimate of non-OPEC supply for the whole of 2002 to 47.36 million bpd, still 87,000 bpd more than 2001.
OPEC agreed its latest quota cut only after receiving assurances of a simultaneous 462,500 bpd reduction by non-OPEC countries Norway, Russia, Mexico, Oman and Angola.
From the fourth quarter 2001 to the first quarter 2002, OPEC expected non-OPEC supply to rise by 40,000 bpd to 47.10 million bpd, then to fall by 220,000 bpd in the second quarter.
OPEC's world oil demand estimate for this year was unchanged at 76.2 million bpd - a growth of 300,000 bpd from 2001.
The call on OPEC crude oil this year would be 25.6 million bpd, 500,000 bpd below last year, assuming no change in stocks.