Considering that, say, 100% of tech employees are consumers and CPI measures cost increases for consumers, it may be “arbitrary” but still highly relevant.
For instance, if my employees are earning 500k+ and driving Teslas, I don't think the price of oil, lettuce and tomato, and even general rental market would be materially impactful like, say, the increase in Los Altos home prices.
What really makes a difference is how much a competitor is willing to pay, their scale, their work environment, and how well they sell themselves.
