Dear Michael,
This has come to be known as the Tinbergen Norm. From what I can tell, this is the source:
Tinbergen, J. 1975. Income Distribution: Analysis and Policies. Amsterdam: North- Holland. 170 pp.
Yours,
Esther-Mirjam
______________________________________________________________________
Professor of Economic Theory and Policy, Radboud University Nijmegen
Member, Senate of the Netherlands
http://www.emsent.nl