Subject: Re: [bitcoin-dev] "A Transaction Fee Market Exists Without a Block Size Limit"--new research paper suggests

From: Dave Hudson <[email-masked]>
Date: Tue, 4 Aug 2015 11:41:53 -0700

The paper is nicely done, but I'm concerned that there's a real problem with equation 4. The orphan rate is not just a function of time; it's also a function of the block maker's proportion of the network hash rate. Fundamentally a block maker (pool or aggregation of pools) does not orphan its own blocks. In a degenerate case a 100% pool has no orphaned blocks. Consider that a 1% miner must assume a greater risk from orphaning than, say, a pool with 25%, or worse 40% of the hash rate.

I suspect this may well change some of the conclusions as larger block makers will definitely be able to create larger blocks than their smaller counterparts.

Cheers,
Dave

> On 3 Aug 2015, at 23:40, Peter R via bitcoin-dev <[email-masked]> wrote:
> 
> Dear Bitcoin-Dev Mailing list,
> 
> I’d like to share a research paper I’ve recently completed titled “A Transaction Fee Market Exists Without a Block Size Limit.”  In addition to presenting some useful charts such as the cost to produce large spam blocks, I think the paper convincingly demonstrates that, due to the orphaning cost, a block size limit is not necessary to ensure a functioning fee market.  
> 
> The paper does not argue that a block size limit is unnecessary in general, and in fact brings up questions related to mining cartels and the size of the UTXO set.   
> 
> It can be downloaded in PDF format here:
> 
> https://dl.dropboxusercontent.com/u/43331625/feemarket.pdf <https://dl.dropboxusercontent.com/u/43331625/feemarket.pdf>
> 
> Or viewed with a web-browser here:
> 
> https://www.scribd.com/doc/273443462/A-Transaction-Fee-Market-Exists-Without-a-Block-Size-Limit <https://www.scribd.com/doc/273443462/A-Transaction-Fee-Market-Exists-Without-a-Block-Size-Limit>
> 
> Abstract.  This paper shows how a rational Bitcoin miner should select transactions from his node’s mempool, when creating a new block, in order to maximize his profit in the absence of a block size limit. To show this, the paper introduces the block space supply curve and the mempool demand curve.  The former describes the cost for a miner to supply block space by accounting for orphaning risk.  The latter represents the fees offered by the transactions in mempool, and is expressed versus the minimum block size required to claim a given portion of the fees.  The paper explains how the supply and demand curves from classical economics are related to the derivatives of these two curves, and proves that producing the quantity of block space indicated by their intersection point maximizes the miner’s profit.  The paper then shows that an unhealthy fee market—where miners are incentivized to produce arbitrarily large blocks—cannot exist since it requires communicating information at an arbitrarily fast rate.  The paper concludes by considering the conditions under which a rational miner would produce big, small or empty blocks, and by estimating the cost of a spam attack.  
> 
> Best regards,
> Peter
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