Bitcoin transaction fee rules

One conclusion drawn by Kroll and his Princeton colleagues Ian Davey and Ed Felten is that those rules will have to be significantly changed if Bitcoin is to last. Their models predict that interest in “mining” for bitcoins, by downloading and running the Bitcoin software, will drop off as the number in circulation grows toward the cap of 21 million set by Nakamoto. This would be a problem because computers running the mining software also maintain the ledger of transactions, known as the blockchain, that records and guarantees bitcoin transactions (see “What Bitcoin Is and Why It Matters”).

Miners earn newly minted bitcoins for adding new sections to the blockchain. But the amount awarded for adding a section is periodically halved so that the total number of bitcoins in circulation never exceeds 21 million (the reward last halved in 2012 and is set to do so again in 2016). Transaction fees paid to miners for helping verify transfers are supposed to make up for that loss of income. But fees are currently negligible, and the Princeton analysis predicts that under the existing rules these fees won’t become significant enough to make mining worth doing in the absence of freshly minted bitcoins.

The only solution Kroll sees is to rewrite the rules of the currency. “It would need some kind of governance structure that agreed to have a kind of tax on transactions or not to limit the number of bitcoins created, ” he says. “We expect both mechanisms to come into play.”

That kind of approach is common in established economies, which tame things like insider trading with laws and regulatory agencies and have central banks to shape economies. But many backers of Bitcoin prize the way it currently operates without centralized control, and would likely rebel at any suggestion of changing the rules.