This working paper published by OECD is well worth a read. Check it out!
via Trends in Top Incomes and their Taxation in OECD Countries | OECD READ edition.
The graphs, in the paper, highlighs income inequality in both the US and the UK being significantly ahead of other leading countries.
Personally, I believe that income inequality has become more acute since the financial crisis of 2008. The wealthy have seen their wealth rebound since 2008 but the working and middle classes have been severely squeezed by excessive austerity.