Progress, far from consisting in change, depends on retentiveness …. Those who cannot remember the past are condemned to fulfil it.
—George Santayana, 1905-06
Those who are familiar with the “equal proportions” formula used to reapportion the U.S. House of Representatives each decade are aware how sensitive it is to small changes in states' population data. In 1990, this sensitivity took on new significance as statisticians and politicians debated the merits of adjusting the decennial census data to correct for the differential undercount. The “official” apportionment results from the 1990 Census were published in December 1990, and the reapportionment of Congressional seats among the states proceeded on the basis of those data. Adjusted census results were released in July 1991. These data would have changed the reapportionment of Congress and shifted two seats in the House: one each from the states of Wisconsin and Pennsylvania to the states of California and Arizona.
Adding to the complexity of the debates about which set of data to use, and in the midst of the ensuing litigation between New York City and the U.S. Department of Commerce, the Census Bureau discovered a computer coding error in the adjusted data estimates and issued “revised adjusted data” in January 1992.