But they also did pretty obviously do it in part to increase their profits.
The cartel was formed in part as a response to the volatility of the lightbulb market (there was so much competition it was difficult for any company to stay dominant or to maintain stable/predictable profits), and was followed by a large increase of sales for the cartel's members.
Short of long-term environmental costs (which nobody was seriously worrying about in the early 1900s), there's very little reason to standardize the light output, efficiency, and lifespan of a bulb, which could instead be determined by consumer choice in a free market.
If the Pheobes Cartel was simply setting labeling standards, maybe it would be debatable whether or not there was any bad intention. But it remains a good example of planned obsolescence in part because of the excuses engineers used at the time, which were pretty clearly not the entire reason for cartel's formation, but were used to dismiss criticism of reduced competition.
It's a good lesson for people to learn: planned obsolescence is usually accompanied by a couple of engineering reasons for the tradeoffs, and sometimes those tradeoffs are justifiable in a vacuum. But planned obsolescence removes the ability for the consumer to choose their own tradeoffs and to optimize for their own needs, and instead it prioritizes making specific technical tradeoffs that just coincidentally happen to benefit the company's bottom line.
> The cartel lowered operational costs and worked to standardize the life expectancy of light bulbs at 1,000 hours[6] (down from 2,500 hours),[6] and raised prices without fear of competition. The cartel tested their bulbs and fined manufacturers for bulbs that lasted more than 1,000 hours.
The simple fact that they explicitly set a lower operational life target rather than setting a minimum target tells me everything I need to know about what they were trying to do. The additional fact that they fined manufacturers who exceeded the target doesn't leave much room for speculation.
If they had any interest whatsoever in efficiency as the driver, the targets would have been based on an efficiency target like lumens per watt rather than life expectancy.
> Some engineers deemed 1,000 hours a reasonable figure to balance the various operational aspects of an incandescent bulb, since longer lifespan means reduced efficacy (lumens per watt): a longer-life bulb of a given wattage puts out less light (and therefore proportionally more heat) than a shorter-life bulb of the same wattage. Nevertheless, long-life incandescent bulbs were and are available with lifespan ratings up to 2,500 hours, and these do in fact produce less light per watt.
What I was trying to say in my previous comment was that while there was a cartel which did reduce the lifetime of commonly-used light bulbs, they didn't do it solely to increase their profits - there was an actual technical tradeoff involved, and they chose a figure which provided (in their opinion) a good balance of all the involved parameters. That's what always gets forgotten when this story is mentioned.