Lang et al (2010) find a worldwide trend towards greater comparability, including for mandatory IFRS adopters. The global trend presumably reflects, among other things, convergence around the world towards IFRS even in countries that do not adopt it. As for the US, the largest non-adopter, IFRS and US GAAP have been moving closer since the 1990s. And
for Singapore, which Lang et al (2010) classify as a non-adopter, local GAAP has since 2003 been so close to IFRS that some researchers treat it as a mandatory IFRS adopter from that date.