  Ethereum introduced Transaction Access Lists (TALs) in 2020 to optimize gas
costs during transaction execution. In this work, we present a comprehensive
analysis of TALs in Ethereum, focusing on adoption, quality, and gas savings.
Analyzing a full month of mainnet data with 31,954,474 transactions, we found
that only 1.46% of transactions included a TAL, even though 42.6% of
transactions would have benefited from it. On average, access lists can save
around 0.29% of gas costs, equivalent to approximately 3,450 ETH (roughly US$ 5
Mio) per year. However, 19.6% of TALs included by transactions contained
imperfections, causing almost 11.8% of transactions to pay more gas with TAL
than without. We find that these inaccuracies are caused by the unknown state
at the time of the TAL computation as well as imperfect TAL computations
provided by all major Ethereum clients. We thus compare the gas savings when
calculating the TAL at the beginning of the block vs. calculating it on the
correct state, to find that the unknown state is a major source of TAL
inaccuracies. Finally, we implement an ideal TAL computation for the Erigon
client to highlight the cost of these flawed implementations.
