Comment by bombcar

It would be interesting (but perhaps useless) to try to weigh the companies by the percentage associated with whatever index or group you're trying to build - e.g, if you're building an IT Index, and AMZN makes 50% of revenues (or profit or however you'd value "that side" of the business) - you'd deweight them by half.

So if by market cap they'd be 8% of the index, you'd have them at 4%, because half of what they do isn't IT but something else (logistics, retail).