Ascription is an Anathema to any Enthusiasm is one of my favorite blogs. In the latest installment on income distribution, he links to this bimodal distribution of starting lawyer salaries.
If the chart were a flipbook of the last twenty years, the first mode would be relatively stationary, barely tracking inflation, while the second mode would be moving quickly to the right--i.e., the salary wars. In fact, because of the recent jump to $160K in the major markets, the second mode has already moved even more to the right.
I'm sure this is true for other occupations, too. This is important for lots of reasons, but as Wikipedia explains:
Bimodal distributions are a commonly-used example of how summary statistics such as the mean, median, and standard deviation can be deceptive when used on an arbitrary distribution. For example, in the distribution in Figure 1, the mean and median would be about zero, even though zero is not a typical value. The standard deviation is also very large, even though the deviation of each normal distribution is relatively small.
When talking about the economy, wealth, and class, it's important to understand the data. When people say that the average income has increased over the past 20 years, I suspect the vast majority of the gains have gone to the few at the top.
