More precisely, if we may recall it here, several curves, referring to different periods and with quite a few hints that the relationship was anything but stable. The article ended with the following words: ‘These conclusions are of course tentative. There is need for much more detailed research into the relations between unemployment, wage rates, prices and productivity’.
More than sixty years on, it cannot be said that the author’s wish has not come true; there must be thousands of empirical papers on the Phillips curve.