Because many countries are producing less than than they used to - and the other countries can't increase their output enough to keep up with demand.
That's false on several levels. A few oil producing countries have claimed that there is enough supply for demand (SA & Iran most notably). Nobody said anything about whether world wide oil supply is increasing, decreasing, or staying the same.
Look at this graph from the CFTC report - oil supply is not keeping up with economic growth as it did before 2005.
http://www.theoildrum.com/files/CFTC_Fig_1.pngActually you have it backwards. I want to be wrong. A world where oil production is decreasing by 4-5% every year ain't going to be fun. But, none of the hard data show that we're going to escape that fate.
I don't understand what you're saying - are you saying the reports are wrong? I haven't heard any evidence of that - and all the corrections for supply and reserve reports for the last year have all been revised downward.
You are right - historically saudi arabia has been a swing producer that is able to increase supply at the drop of a hat to decrease prices. But, this spring they at first declined to increase supply when Bush pressured them. Then they agreed to a piddly 2-300,000 barrels per day increase.
Their recent behavior only makes sense if they no longer have millons of barrels of spare capacity like they did in the good ole days. And actions speak louder than words. The Saudi oil minister is about as credible as the Iraqi press secretary who claimed Bagdhad was safe from attack as the US tanks rolled in behind him.
They have every reason not to admit that they are producing all out. It means they have lost a lot of power in the world and in their own country. The SA regime is not politically stable - if they can no longer guarantee that the oil money will keep flowing there is an increased chance of revolution. The Saudi's treat their oil field data as a state secret.
As for your comment about oil producing nations "using" less - actually all the wealth being poured into those countries are causing them to increase their oil consumption. Meaning that even if they kept pumping out the same amount their net exports are declining.
That's like saying gravity is unwarranted - what we saw was markets acting the way markets are supposed to act.