One of my favorite authors on the visual display of information is Edward Tufte. Besides despensing great advice on presenting data, he’s produced a series of beautiful books. They’re really picture books for the data nerd set.
I think he’d like this diagram:
The only thing better would be to figure out how to plot the whole density for each year. The black lines give preference for the selected percentiles, but there’s no a priori reason to think the 99 percentile is some how more important than the 96 percentile. Because this bias is built in, the diagram is a little misleading.
But I like it, nonetheless.
If you read through the comments at Prof. Kenworthy’s post, you’ll see many people committing the fallacy of assuming the same individual is represented by a single percentile line on the chart. As I’ve pointed out before, people do not stay within the same percentile (or decile or quintile, etc) over their lives. The churn of poverty is very high. Before age 75, for example, 50% of Americans will have spent some time below the poverty line and 50% spent some time at level of income ten times the poverty line. Only about 20% of Americans won’t experience one of these extremes.
UPDATE: Yes, Nancy, that means 30% of Americans will have been rich and poor in their lifetimes.
UPDATE 2: I swear to all that is holy that I titled this post before reading the post over at CT.
UPDATE 3: These Sala-i-martin (2002) charts are an improvement, except for the log scale, on the Kenworthy ones: