http://koreatimes.co.kr/www/news/biz/2012/11/488_125858.html
This is basically a summary of the data presented in the article.
~Pay gap in OECD countries from 2000 to 2012~
Japan: 34% to 29%
US: 23% to 19%
Israel: 28% to 21%
South Korea: 40% to 39%
~Current Pay gaps in other OECD countries~
Canada: 19%
Finland: 19%
Switzerland: 19%
Austria: 19%
Belgium: 9%
Norway: 8%
New Zealand: 7%
Hungary: 6%
Poland: 6%