Over 2014 global oil demand grew by a much weaker than expected 0.7 per cent, or 600,000 barrels a day, the International Energy Agency says.
Supply, on the other hand, climbed. The United States alone increased its output by 1.6 million barrels a day, according to US Energy Information Administration data, dwarfing the additional 1 million barrels a day from the next four largest contributors to supply growth (which included, surprisingly, Iraq).
And, crucially, Saudi Arabia has chosen to abandon its traditional role as the swing producer, willing to cut production in times of excess demand to stabilise the price.
The Opec cartel voted in late November to leave its collective ceiling target of 30 million barrels a day unchanged.
The International Monetary Fund reckons the net effect of the oil price collapse will be a shot in the arm for the world economy, adding between 0.3 and 0.7 per cent to global gross domestic product, compared to what it would be without the drop in oil prices.
The Reserve Bank has estimated that if oil prices remain around US$50 a barrel it will shave more than $2 billion off New Zealand's import bill and boost households' average disposable income by around $600 a year, all else being equal.
Internationally, so far the main effects of the price slump have been on the supply side.
"Companies have been taking an axe to their budgets, postponing or cancelling new projects while trying to squeeze the most out of producing fields," the IEA says. The supply effects of that will be felt down the road.
On the demand side it sees little impact yet and expects only a modest increase this year, of 900,000 barrels a day, or around 1 per cent.
"That is because the usual benefits of lower prices - increased household disposable income, reduced industry input costs - have been largely offset by weak underlying economic conditions, which have themselves been a major reason for the price drop in the first place."
The IEA's best guess is that the market will begin to get back into balance between supply and demand in the second half of this year.
But that does not mean a return to the status quo ante, it warns: "It is clear that the market is undergoing an historic shift.
"Opec's embrace of market forces last November is a game changer. So is the US light, tight [shale] oil revolution."
Though rationalisation of the US shale oil industry may be under way, with highly leveraged firms vulnerable, the IEA argues that thanks to its short lead time and low up-front capital costs, it may prove faster to ramp up production than conventional oil operations.
The caveat to the foregoing prognostications, however, is that oil is not an ordinary commodity where the price is all about supply and demand and the marginal cost of production. Political factors are crucial, too.
International oil prices are of vital economic and fiscal importance to oil exporting countries.
So a key uncertainty is how long Opec can live with prices this low.
Even in Saudi Arabia, where the physical cost of pumping oil from its giant fields is a few dollars a barrel, the "fiscal break-even" price is estimated to be more than US$100 a barrel. The break-even price is the price at which an oil exporting country balances its budget.
The IMF cites estimates for Middle Eastern and Central Asian producers' break-even prices this year which range from around US$50 a barrel for Kuwait to more than US$120 for Iran. Most are north of current market prices.
It is a fair bet that the pain thresholds for more populous exporters elsewhere, like Russia, Nigeria and Venezuela, have been crossed too.
To a degree the fiscal impact of lower oil prices can be mitigated through a lower exchange rate (though there are costs to that too, and some petro-economies have fixed exchange rate regimes).
Some oil exporters have large sovereign wealth funds they might draw down, as well as a capacity to borrow.
But it is hard to see current prices as politically sustainable within the councils of Opec. At some point the Saudis and their Gulf allies may have to weigh the perceived benefits of their policy against the risk of a break-up of the cartel.
Similarly, you have to wonder how much damage to its shale oil industry the United States is prepared to tolerate. Its spectacular growth has, after all, brought the US a long way back towards self-sufficiency. How long before calls emerge for a protective tariff, perhaps offset by a cut to domestic taxes on oil to limit the impact at the pump?
Globally the oil industry spends hundreds of billions of dollars a year searching for oil and bringing it on stream. That is a lot of jobs, profits and vested interest generally.
How compressible is that spending before a political backlash sets in?
Finally, there are strategic considerations. A policy that looks to the Saudis like defending their market share can look to the rest of the world like increased reliance on a country, two of whose neighbours - Iraq and Syria - are racked by vicious civil war while another, Yemen, is a failed state heading the same way.
