OPEC has produced ~40% of the world oil supply for several decades. The only times it significantly produced less, was when they chose to drive prices higher by producing less oil, until the demand market caught back up.
Their "strength" in market share is essentially unchanged. But their ability to work together seems to have diminished, although they have often disagreed over the decades.
From the article: “For the first time in a long time, the ability to determine the price of oil no longer clearly resides with OPEC. Instead, it’s increasingly U.S. producers at the controls.”
Wow. Amazing statistic.
Looked at another way, this means that SA has had several decades to become thoroughly hooked on petrodollars.