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I don't know the answer to the first question. The second question (Is there ever an reason to mine 0-fee transactions?) is "yes, for a while". Until approxima

I don't know the answer to the first question. The second question (Is there ever an reason to mine 0-fee transactions?) is "yes, for a while". Until approximately 2040 new Bitcoin are introduced into the system as a reward to the miner who discovers a block. So, even if a miner mines a block with only 0-fee transactions, they are still rewarded with a small amount of Bitcoin "from nowhere". Bitcoin will be introduced in this manner until there are 21 million BTC in existence, at which point they will stop being introduced "from nowhere". This is expected to take until about 2040 (though I don't know how that projection is made). After that point there won't be much of an incentive to mine 0-fee transactions.

tlrobinson 9y ago
> So, even if a miner mines a block with only 0-fee transactions, they are still rewarded with a small amount of Bitcoin "from nowhere". Sure, but as long as there are transactions with fees in the mempool, then mining 0-fee transactions has an opportunity cost. Currently that's about 5 BTC per block, compared to the 12.5 BTC reward (https://www.smartbit.com.au/charts/transaction-fees-per-block https://www.smartbit.com.au/charts/transaction-fees-per-bloc...). It's possible that forgoing the transaction fees will make mining for you unprofitable if margins are thin. Also, larger blocks are more likely to be orphaned, so including 0-transaction fees increases that risk (very slightly) with no additional reward (though currently the orphan rate appears to be basically zero, even with full blocks)
umanwizard 9y ago
But why include those transactions in the block at all? It’s perfectly valid to mine a block containing no transactions other than the block reward.
yincrash 9y ago
Difficulty of mining is adjusted every 2016 blocks to maintain a rate of one block per 10 minutes, so since the rate of block generation is set, and the reward shrinking rate is also set, you can predict when all bitcoin have been mined.

tlrobinson 9y ago

> So, even if a miner mines a block with only 0-fee transactions, they are still rewarded with a small amount of Bitcoin "from nowhere". Sure, but as long as there are transactions with fees in the mempool, then mining 0-fee transactions has an opportunity cost. Currently that's about 5 BTC per block, compared to the 12.5 BTC reward (https://www.smartbit.com.au/charts/transaction-fees-per-block https://www.smartbit.com.au/charts/transaction-fees-per-bloc...). It's possible that forgoing the transaction fees will make mining for you unprofitable if margins are thin. Also, larger blocks are more likely to be orphaned, so including 0-transaction fees increases that risk (very slightly) with no additional reward (though currently the orphan rate appears to be basically zero, even with full blocks)

umanwizard 9y ago

But why include those transactions in the block at all? It’s perfectly valid to mine a block containing no transactions other than the block reward.

yincrash 9y ago

Difficulty of mining is adjusted every 2016 blocks to maintain a rate of one block per 10 minutes, so since the rate of block generation is set, and the reward shrinking rate is also set, you can predict when all bitcoin have been mined.