As I explained upthread, moving between pools doesn't necessarily enable decentralization, because marginal cost of mining will dictate that miners MUST seek out a pool with significant portion of the system PoW hashrate, otherwise the miner will be unprofitable. For the professional miners not at the margins of profitability, they are already centralization.
Well, I don't have numbers on profitability of mining, will stop this dispute.
I believe it can be shown to be a insoluble mathematical fact that the distribution of profitability of mining will not be uniform and will be more Gaussian-shaped distributed. Thus the more decentralized the miners (in a mining for profit design such as Satoshi's design), the greater the need for the additional profitability of less variance of rewards.