None of which is evidence that a cartel was necessary to enforce different standards; consumer preference would have solved that problem on its own. Power effi

None of which is evidence that a cartel was necessary to enforce different standards; consumer preference would have solved that problem on its own. Power efficiency problems only require cooperation to solve in instances where the downsides aren't immediately visible to the consumer (ie, long-term decreased power costs, labeling, environmental costs). But people definitely weren't worried about environmental efficiency of light bulbs when the Phoebus Cartel started up. For consumer-visible deficiencies (as in literally how much visible light a lightbulb produces), you don't need collusion to convince consumers to make the switch to a clearly (pun intended) better product. It's worth noting just how janky and circuitous these standards were as a way of increasing efficiency, given that Phoebus Cartel had perfectly good measures for efficiency that they could have targeted instead. There were not rules for minimum lumens, or max wattage, or minimum efficiency; there were only rules on maximum lifespan. In fact, for their "class B" category of lamps, not only did the Phoebus Cartel not impose minimum efficiency measures, they actually included an upper bound on how efficient Class B lamps were allowed to be. I think it's extremely unlikely that the Phoebus Cartel was primarily worried about the environmental costs of inefficient light bulbs, and I think it's extremely unlikely that in the absence of a cartel consumers would have been unable to tell the difference between a dim lightbulb and a bright one when making purchasing decisions. The most likely explanation of their behavior is the simplest one; they set constraints designed to maximize profits and decrease the risk of large competitors out-innovating each other, and then designed engineering optimizations and standards to fit into those constraints, not the other way around.