Misleading Line Graphs

Property When there is a large gap between data values, a graph may use a broken axis. On a graph with a broken axis, the scale on an axis is interrupted, often to avoid showing a large empty space from zero to the first data point.

Examples A stock price increases from 102 dollars to 108 dollars. A broken axis starting at 100 makes this 6 dollars jump look like a gigantic leap. Website visits go from 10,500 to 11,000 in a month. If the y axis starts at 10,000, the graph will show a steep, impressive climb. A graph shows a company's profit grew from 1.2 million dollars to 1.3 million dollars. Using a broken axis from 1 million makes the growth seem enormous.

Explanation Think of a broken axis as a visual trick to make a molehill look like a mountain! By chopping out the bottom of the graph, tiny changes suddenly appear huge and dramatic. It’s a great way to make a small increase in sales look like a massive success story, even if the real change was quite small.