[1][2] In his youth Mandelbaum was involved with leftist politics and had several years at the Frankfurt School for Social Research.
During the war worked with allied intelligence and subsequently joined the Oxford Institute of Statistics.
[3] This small book which was to become one of core texts for the new discipline, stressed In 1950 he moved to Manchester and with his colleague W. Arthur Lewis helped establish the Department of Economics at the University of Manchester as a major centre in Development Economics research and teaching.
After retiring from Manchester he worked for a further seventeen years at the Institute of Social Studies at The Hague.
In general these economists doubted the usefulness of neoclassical economics with its presumptions of smoothly operating markets and saw the role of the state as being key to the development process.