In the world of OPEC, the word production can mean different things. There is official production, whereby OPEC sets quotas for individual members under an overall volume, and there is actual production, which can bear little resemblance to official levels.
And there is a further complication. OPEC, although it has given out the overall target number for the current output agreement, has not published the individual quotas under that target. Which means that people like my colleagues and myself have had to work out those quotas by ourselves, sometimes with a bit of help from delegates or ministers who may confirm figures or indicate that our calculations are close to the mark.
It would, of course, be so much easier if OPEC just published the figures.
I'll investigate what recent OPEC quotas have been later on, if they don't update these numbers themselves; for now, here's my chart:
I'd post it full size but aren't having luck getting the resolution right at smaller sizes, and full size it covers a lot of the page, including the sidebar.
Lots of cheating in the 80s, as widely reported in the news; they showed little interest in bringing the price up for a few years there, but actively defended the $20/bbl ceiling thereafter. The spike in quota in Jan '98 is odd, I'd guess this was in response to the Asian financial crisis which kicked off in July '97, but wouldn't that crater demand? All of this with a trend towards falling prices. John Williams at WTRG explains thusly:
OPEC continued to have mixed success in controlling prices. There were mistakes in timing of quota changes as well as the usual problems in maintaining production discipline among its member countries.
The price increases came to a rapid end in 1997 and 1998 when the impact of the economic crisis in Asia was either ignored or severely underestimated by OPEC. In December, 1997 OPEC increased its quota by 2.5 million barrels per day (10 percent) to 27.5 MMBPD effective January 1, 1998. The rapid growth in Asian economies had come to a halt. In 1998 Asian Pacific oil consumption declined for the first time since 1982. The combination of lower consumption and higher OPEC production sent prices into a downward spiral. In response, OPEC cut quotas by 1.25 million b/d in April and another 1.335 million in July. Price continued down through December 1998.
Prices began to recover in early 1999 and OPEC reduced production another 1.719 million barrels in April. As usual not all of the quotas were observed but between early 1998 and the middle of 1999 OPEC production dropped by about 3 million barrels per day and was sufficient to move prices above $25 per barrel.
Then in July '98 Iraq no longer took part in OPEC quotas. This was in the era of the Oil-for-Food Programme; in the wake of Gulf War I Iraq's quota was ca. 500 kb/d from Oct '91 for exactly two years, then was bumped up to 1200 kb/d for some reason, and to 1314 kb/d for Jan '98, while production hovered around 550 kb/d until Dec '96.
Note how the dates of OPEC changes in quota (which I've marked in bold on the spreadsheet) don't match what Williams mentions in his analysis; also OPEC list a production shift of some kind for July '98 on their page, highlighting a bunch of small numbers in yellow; I've discarded these on my sheet.
The drop in OPEC production in Jan '94 is an artifact of the EIA numbers, at the transition between the quarterly data I dug up, and the monthly numbers which begin here. The quarterly numbers are definitely all liquids, but for some reason the monthly numbers are much lower; still, the shape of the curve conveys the general idea. Perhaps the monthly numbers don't include Iraq, and also Gabon left OPEC in '94 but they were only producing 340 kb/d, and as stated above Iraq wasn't cranking out much either; the drop in the data is almost 4 mb/d. Odd!