Historically, most non-OPEC producers have taken advantage of OPEC's voluntary production restraint by increasing their own production whenever possible. As a result, the market share of non-OPEC producers rose for a number of years, but oil prices remained at relatively low levels and the markets were less stable than they could have been.

However, the oil price slump of 1998 and early 1999 reinforced OPEC's constant message that oil market stability can only be achieved through co-operation between OPEC and non-OPEC oil producers. In support of OPEC's efforts to restore stability to the oil market by restraining output, several non-OPEC oil producers also cut their production, thus helping prices recover from the slump. These countries included Mexico, Norway, Oman, and Russia.