If you are like me, you struggle with supply and demand curves. Maybe it’s because I am used to drawing curves in mathematics, which are different than these curves, which tend to show a ‘before and after’ of where the curve shifts to on the graph when the price changes or the quantity changes. That change in price or quantity causes the curve to shift.

To see what I mean, I took these two examples from wikipedia. In these examples, we have right-shifts.

 

A right-shift of demand curve increases both price and quantity. Pretty straightforward: price goes up, quantity goes up. However…

A right-shift of supply curve decreases price and increases quantity. Here the price moves in the opposite direction of the quantity.

In short: with demand, price and quantity go hand in hand while with supply, they move in opposite directions.

P.S.These are supply and demand curves for most goods with elastic supply and demand. The curve changes if you have inelastic supply and demand. And they also change when you have Giffen goods or Veblen goods.