Economics

Choices within a budget, prices within a market

Economics here begins with a limited budget rather than a list of financial terms. Choosing one option means giving up another, and a market price changes the choices available to buyers and sellers. The course develops those ideas through graphs you can adjust. It is an introduction to a model of decisions and markets, not advice about investments. Read each example for the assumptions it holds fixed and the change it asks you to make.

One course with a connected sequence

Supply and demand opens with scarcity and opportunity cost. Demand and the law of demand come next, followed by supply and the law of supply. Only after the two sides have been examined separately does the course bring them together at market equilibrium. This order gives each curve a meaning before you start reading their intersection.

The later units consider shifts in demand and supply, price ceilings and price floors, and a first look at elasticity. Do not skip directly from an intersection to a conclusion about a policy. First ask which curve changes, why it changes, and whether the proposed price control affects the market outcome in the example. Elasticity then adds a question about responsiveness rather than merely the direction of a change.

Separate a movement from a shift

The budget scene lets you compare purchases under a fixed spending limit. In the demand and supply scenes, change the displayed price and inspect the quantity on the relevant curve. The equilibrium scene brings both curves into view. Later controls let you shift the curves, compare market settings and inspect price controls. Write down the starting setting before moving a slider so you can explain what was changed rather than just report the final picture.

The distinction between movement along a curve and movement of the curve is central. A price change and a change in another condition are not the same experiment. The shifts unit discusses income and distinguishes normal from inferior goods, so “higher income means more demand” needs a qualification. Use the example in the unit rather than silently applying one kind of good to every market.

Explain what the graph actually establishes

For a ceiling or a floor, identify the controlled price and compare the quantities demanded and supplied there. For elasticity, explain what response is being compared, not simply whether a line looks steep. Return to opportunity cost when describing a choice: the question is what alternative is given up. The unit questions and summaries help test these distinctions in words as well as on a graph. Before accepting an answer, name the changed input, the outcome shown by the model and the conditions that were kept fixed.