[bad-joke]

The first citation on the page[1] mentions researcher Markus Krajewski who reviewed Phoebus records and concluded "It was the explicit aim of the cartel to reduce the life span of the lamps in order to increase sales [...] Economics, not physics."

Cursory searches of Markus Krajewski yield an IEEE Spectrum article[2] with further references to his work:

> The 2010 documentary The Light Bulb Conspiracy explores the Phoebus cartel as an early example of planned obsolescence and includes interviews with Markus Krajewski. For more on the cartel and planned obsolescence, see the author’s "Fehler-Planungen. Zur Geschichte und Theorie der industriellen Obsoleszenz," in Technikgeschichte, vol. 81, No. 1, p. 91–114, 2014, and "Vom Krieg des Lichtes zur Geschichte von Glühlampenkartellen," in Das Glühbirnenbuch, edited by Peter Berz, Helmut Höge, and Krajewski (Braumüller Verlag, 2011).

Hope this helps!

[1]https://outline.com/JYvASt [2]https://spectrum.ieee.org/tech-history/dawn-of-electronics/t...