[hammock]

>shouldn't things improve for everyone?

Are they not? According to the chart, income growth is positive (things improving) for everyone but those below the 5th percentile.

[TheAdamAndChe]

The income growth for the lower percentages has been below inflation. Combined with the fact that the middle class is shrinking while the lower and upper classes are growing, it means that things aren't improving for many, but growing worse.

[hammock]

Footnote on the chart says the figures are already adjusted for inflation.