small: 7.5" dia x 39"h
large: 17.5" dia x 39"h
lathe turned and ebonized poplar
The small pipe represents the share of the US aggregate income received by the middle 20% of families from 1970, at the bottom of the pipe, to 1995 at the top.
The large pipe represents the share of the US aggregate income received by the top 5% of families from 1970, at the bottom of the pipe, to 1995 on the top.
The numbers represent the "income limits," i.e, the lower of the income range, for each category in constant 1995 dollars. The income range for the middle quintile (20%) of earning families, represented by the smaller pipe, is $48,985 to $72,259 for 1995. The lower number was used in all cases to determine pipe diameter.
The sculpture itself is intended to function formally as well as informationally. No attempt was made to make the pipe diameters, for example, correspond exactly to the income numbers but to be, rather, suggestive of trends. Note especially that the first time increments, at the bottom of the pipes, 1970-75 and 1975-80, are five years long while the remaining increments are one-year intervals. On the sculptures themselves the increments are equal in actual length.
Sources:
Statistical Abstract of the United States
For longer timelines, see Historical Income Tables, U.S. Bureau of the Census; and also...
Daniel Weinberg, "A Brief Look at Postwar Income Inequality"