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December 03, 2015, 01:58:20 AM |
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This is actually a very large and forward-looking topic, tied to the discussion of block size limit
It is forward-looking because currently majority of the miner's income is coming from block reward(25 btc per block), the fee income is neglectable
So you can observe that some chinese mining pools would mine empty blocks to just harvest the block reward and quickly broadcast that empty block to the network (their network speed is slow, if they broadcast a full 1MB block, the chance that block being orphaned will be larger, thus incur a loss for the pool)
Basically, a smart pool will calculate the block orphan risk when including transactions (more transactions will raise the orphan rate due to longer broadcasting time), so today's recommended fee is based on the result of such calculation, not arbitrarily decided
For example, if a full 1MB block containing 2000 transactions will broadcast slower than an empty block, thus raise the block orphan rate by 1%, then the pool will lose 1% of the block reward, which is 0.25 BTC, divided by 2000 transactions, you get 0.000125 btc per transaction, that's the recommended fee right now
For 2MB blocks, the broadcasting time of such a large block might affect the orphan rate more significantly, say raise the block orphan rate to 4%, and now you can include 4000 transactions in each block. As a result, although each block have double amount of transactions, but a full block will cost 4x more for miners, so the fee for each transaction would double
So increase the block size might bring a higher fee, if the network is not fast enough to broadcast a 2MB block worldwide in 10 minutes
And then you have another scenario of fixed block size at 1MB forever. In this case, the transaction capacity is always 2000 transactions per block, people will compete for these limited spaces, and also combine their small transactions into large ones to save the fee. Just like Fedwire system only processes 4 transactions per second, if bitcoin become a system like that, then it will only process large transactions valued more than 1 million dollars, and users would not mind paying thousands of dollars in fee (0.x%)
There is a question: Should miners incentive be raised above block reward long before the block reward drop to zero(even at 4th or 5th halving), or after that?
Currently, due to the block reward, you can not enforce a higher fee for miners, since the miners on today's fast network have very low orphan rate if they include all the 2000 transactions, thus any fee above 0.0001 is good enough for them to happily include it
However, if block is larger and the network speed is limited, miners can not include as many as possible transactions without added orphan cost, then I guess the fee will rise when blocks grow beyond certain size
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