FILE PHOTO: A model of an oil pump is seen in front of the OPEC logo in this illustration taken January 9, 2026. REUTERS/Dado Ruvic/Illustration/File Photo Purchase Licensing Rights, opens new tab LONDON, May 27 (Reuters Breakingviews) - In the 1990s, investors learned to place their faith in the “Greenspan put”. The theory was that then-Federal Reserve Chair Alan Greenspan would cut interest rates if markets sagged, propping up global asset prices.