> Ideally you would want to normalize by revenue from government contracts

I'm not sure that makes sense; normalizing by revenue tells the tale of how much of what the company brings in is devoted to swaying public policy, but I'm not sure what normalizing by revenue from government contracts get you -- presumably, any profit maximizing corporation trying to sway policy is trying to do so for its own benefit, whether the way in which it hopes to receive that benefit is by direct government contracts, or by government policy encouraging (and perhaps even subsidizing) others to purchase the service it sells, or by some other shift in policy that helps the firms business.

It makes sense because some companies see lobbying as an investment in future sales, either indirectly through policy or directly.

HP is a prime example of this, as many government computers and services involve HP, hence HP has such a high "investment" rate with lobbying.