And by harder, I'm also including the costs for infrastructure. With futures, you can pretty much focus on just a few exchanges, but with stocks it seems like you need infrastructure for multiple exchanges, multiple fees, and have more routing decisions to make, more communications infrastructure, etc. This is more of an opinion question on the economics and difficulty of the problem. I'm not sure there's a right or wrong answer. I am just seeking opinions about the degree of difficulty, barriers to entry, etc.