Kevin Donoghue has the evidence on that one:
"That's Snowdon & Vane, referring to the years 1931-35. Original source they cite is Deutscher, "RG Hawtrey & the Development of Macroeconomics."
But 1931-35 was Hayek's peak as a macro man. In 1920-30 he failed to make the top 10 (Keynes squeaked in at 10th). In 1936-39 Hayek was joint 7th, trailing Keynes, Robertson, Hicks, Pigou, Harrod and Hawtrey. In 1940-44 he again dropped out of the top 10."Tyler Cowen also notes Alvin Hansen's assessment of Hayek's importance in real time - which I consider to be much more valuable an indicator than Hicks's statements decades later. Hansen of course was not predisposed to attribute much value to Hayek's work since he is generally associated with secular stagnation and long-wave type ideas about the business cycle.