  Decentralization is widely recognized as a crucial characteristic of
blockchains that enables them to resist malicious attacks such as the 51%
attack and the takeover attack. Prior research has primarily examined
decentralization in blockchains employing the same consensus protocol or at the
level of block producers. This paper presents the first individual-level
measurement study comparing the decentralization of blockchains employing
different consensus protocols. To facilitate cross-consensus evaluation, we
present a two-level comparison framework and a new metric. We apply the
proposed methods to Ethereum and Steem, two representative blockchains for
which decentralization has garnered considerable interest. Our findings dive
deeper into the level of decentralization, suggest the existence of
centralization risk at the individual level in Steem, and provide novel
insights into the cross-consensus comparison of decentralization in
blockchains.
