Gender pay gap largely depends on having at least one child

[Major Nikon]

Country -- No children / At least one child

• Ireland -17 14
  
• Australia -3 19
  
• Luxembourg -3 22
  
• Netherlands -2 6
  
• Slovenia 0 16
  
• France 0 12
  
• Mexico 0 17
  
• Germany 2 25
  
• Norway 2 21
  
• Italy 4 3
  
• Iceland 5 19
  
• Hungary 5 15
  
• Belgium 6 10
  
• Canada 7 29
  
• OECD 7 22
  
• Portugal 7 24
  
• United States 7 23
  
• United Kingdom 7 21
  
• Finland 7 22
  
• Poland 9 22
  
• Chile 9 20
  
• Denmark 10 20
  
• Austria 10 23
  
• Greece 10 19
  
• Spain 12 14
  
• Korea 13 46
  
• Sweden 13 21
  
• Czech Republic 13 29
  
• Slovak Republic 14 26
  
• Japan 24 61
  
• Estonia 26 36
  

http://dx.doi.org/10.1787/888932676127

There are a number of factors (other than illegal discrimination) which cause the gender pay gap. Currently the BLS lists the raw gender pay gap for weekly earnings of men and women at 19.4%.
http://www.bls.gov/news.release/wkyeng.t01.htm

Due to misleading representation of the raw pay gap, some seem to think all of the 19.4% is due to illegal discrimination. This ignores relevant socio-economic factors like union representation, hours worked, overtime worked, industry selection, tenure, favoring fringe benefits over pay, wage and salary negotiation.

What's interesting is that in Sweden (bastion of feminism), the raw pay gap is actually higher than the US and when part time workers are considered, the gender pay gap is a whopping 35%.
http://www.thelocal.se/20121107/44276