OPEC members' own versions of their oil output were for years greeted with such skepticism that the group resorted to publishing what others thought they were producing.
That gave rise to a mini-industry of OPEC watchers, tapping secretive sources to track every barrel. Output was hotly contested when the group squabbled over member quotas, which have since been abandoned.
But on Monday, OPEC issued a set of production figures as reported to its Vienna Secretariat by member-countries, without any countries missing from the total for the first time in months.
These also showed the difference between OPEC output based on member-countries' own submissions, and that provided by OPEC's list of secondary sources, which include consultants and industry media, to be narrowing.
"I can see some countries trying to address these problems and publish better data," said an oil market expert working for a European government. "But there are a few countries that I doubt have made much progress."
As OPEC accounts for the bulk of the world's oil exports, its production level is vital information for traders, consumers and governments. The trouble is that finding that number is no easy task due to a dearth of timely official information.
Due to that challenge, the Organization of the Petroleum Exporting Countries since 2012 in its monthly report has published two sets of numbers - one from member-countries themselves, and one from the secondary sources.
The two often show wide differences. But the gap between their OPEC output total has now narrowed to about 230,000 barrels per day (bpd) in the February 2015 estimates published on Monday, from almost 1 million bpd in the first data set given in 2012.
The change could reflect efforts by OPEC and other government agencies to improve the transparency of oil markets through programs such as the Joint Organizations Data Initiative (JODI), and comes at a time when OPEC is defending market share from rival suppliers.
There is little disagreement over the output rate of top producer Saudi Arabia, which told OPEC it pumped 9.64 million bpd in February while the secondary sources estimated 9.68 million bpd.
"We are at a serious moment with OPEC defending market share," said the oil market expert. "It makes sense to be transparent."
The figures still show some long-standing output claims by OPEC members to be pumping at different levels than estimated by the secondary sources.
For example, Venezuela told OPEC it pumped 2.74 million bpd in February, while the secondary sources estimated production at 2.34 million bpd.
And large differences persist. The secondary sources put Iraq's February production 540,000 bpd higher than Iraq itself.
© 2023 Thomson/Reuters. All rights reserved.