OPEC members hold most of the world's spare production capacity, which is what gives the group influence: only a producer able to add barrels quickly can defend a price. Meetings and the quota decisions that follow are the single biggest calendar risk for anyone holding crude futures over a weekend.
Compliance is imperfect and the history is one of repeated cheating, price wars and abrupt reversals. The March 2020 breakdown between Saudi Arabia and Russia flooded the market days before demand collapsed, setting up negative-oil-price-2020.
Example: an unexpected announcement of a 1.0 million barrel per day cut against global demand near 102 million can move crude $3 to $5 in minutes — $3,000 to $5,000 per cl contract, a move most day-trading stops are not built for.
Related: cl, brent, negative-oil-price-2020, super-contango, seasonality