What do supply-demand curves really look like?

Question

In my basic high school economics course, we've always used supply-demand curves that are lines to simplify calculations. In real markets for real goods, what do the supply and demand curves look like? From a mathematical perspective, what would be the concavity, asymptotes, and intercepts?I would imagine the quantity demanded would tend to zero as the price increased to infinity and the quantity demanded would grow very large as the price approached zero, but that is just what my intuition tells me.

Answer 1

It is common intuition. Think of some product like gasoline. at $1,00 /gallon. you will drive all over the place. At $4 per gallon you start to cut back. at $10 you start to carpool to work at $100 you may get rid of your car altogether if not in the short run, perhaps in the log run.

When we estimate demand curves we don't have such wide variation in price and quantity so we can determine slopes and or elasticity in that neighborhood.

Individual supply curves are easy to estimate as costs are measurable . Market supply curves. Like market demand curves are estimated in the neighborhood of observed (price- Quantity pairs) the more variation we have the more precision we will have with or estimates

Answer 2

Very interesting question. This is obviously dependent on the good type (normal or inferior, luxury or necessity), but the real answer is... it's extremely hard to actually draw a real demand curve. Freakonomics actually did an episode on why trying to draw an actual demand curve is near impossible: http://freakonomics.com/podcast/uber-economists-dream/

The gist is: to draw a demand curve, you need to know quantity demanded of a good for everyone in an area for every price level, and it's not a common question that is asked - It would take a lot of time and control (aka ceteris paribus) to derive the demand curve.