Are you trying to suggest that if supply and demand is to explain a price change of 1/3, supply or demand need to have shifted by 1/3 as well? That’s patently false. In some cases, very small changes in supply or demand can result in huge price shifts. In other cases, it will take a huge change to shift prices.
The way you figure it out is to calculate to curves - one curve indicates how much demand there is for the product at any given price. So, just for example, suppose that we’d have the following demand for oil at various prices:
$50 - 95m bbl/day
$75 - 94m bbl/day
$100 - 92m bbl/day
$125 - 87m bbl/day
$150 - 73m bbl/day
The other curve indicates how much supply there is at any given price. Again, let’s suppose the following:
$50 - 82m bbl/day
$75 - 90m bbl/day
$100 - 92m bbl/day
$125 - 93m bbl/day
$150 - 93m bbl/day
The to see what the market price will be, you look for where the curves intersect - in this case at $100. Below that price, not enough oil will be produced to meet demand, and over that price more oil will be produced than there is demand for. But notice a couple things about my example - the demand curve is very steep between $50 and $100. It takes a doubling of the price to shave only a small percentage of the demand off, where as the price increases to $150 the demand drops much more sharply. Of course, these numbers are just made up, but it’s not unreasonable to expect the actual demand curve looks something like that. And on the supply side, notice that while there’s a significant increase in production when you boost the price from $50 to $100, if you push it over $100 you get barely any increased supply. In this case I’m imagining that there simply isn’t any further production capacity available at any price.
Another thing to note is that neither curve is static. In the short term, demand for oil is notoriously inelastic (which means, in economist-speak, that it takes very large price swings to modify demand). This is because most people’s gas consumption is fixed by things like where they live relative to their workplace, and what vehicle they drive. To greatly diminish their use of gasoline requires big decisions that won’t be made at once, so you have to move gas prices a lot to change demand. However, as weeks of high prices turn into months and years, people are replacing their cars and moving their residences, and the higher price will impact their choices and so very slowly we’ll see aggregate demand begin to drop, as noticeable numbers of cars are replaced, etc.
The supply of oil is much more elastic, within certain bounds. Between the old $25/bbl prices and probably about $75/bbl, there’s a very significant amount of production that swings from unprofitable to profitable. There are plenty of wells in this province that get shut off when oil prices drop below a certain threshold (which hasn’t happened for a while now, granted). But past a certain point, you just can’t pump any faster. To increase production beyond that requires huge, long-term projects - prospecting for off-shore deposits or building multi-billion dollar oilsands projects, and the like. And of course, all the while old wells are going dry or at least unprofitable at lower prices.
So, depending on where you are on the two curves, a shift of only a couple percent in demand or supply could double or halve the price of oil, quite easily.