Pam Karlan has posted this draft on SSRN (forthcoming, William and Mary Law Review).  Here is the abstract:

The Constitution requires a decennial “Enumeration” of the U.S. population, following which seats in the House of Representatives are apportioned among the states “according to their respective Numbers.” Congress has enacted a default provision that makes this reapportionment essentially automatic.

It was not always so. The post-2020 round of reapportionment will mark the centennial of the most striking episode in the history of American reapportionment: Congress’s failure, for an entire decade, to reallocate seats in light of the census results. The reasons for this failure, and the consequences of Congress’s ultimate response, continue to shape our politics.

Historians and political scientists have written excellent studies of apportionment that address the nonapportionment post-1920. But none of these studies approaches the question from the perspective of legal doctrine. This essay aims to fill that space. It begins by describing the constitutional structure of apportionment, the questions the Constitution left open, and how those questions were resolved prior to 1920. It then turns to what happened in the 1920s and why. Finally, it explores the judicial response to the 1929 solution and describes how that response set the stage for the Reapportionment Revolution of the 1960s, which imposed a constitutional requirement of equipopulous congressional districts. Along the way, it recovers the lost history of earlier, congressional attempts to require population equality. The story is interesting in its own right, but I also suggest ways in which the upcoming redistricting will occur in a context with striking similarities to the context a century before.