Each of your sources says there is still a gender wage gap in the range of 5-9% after controlling for education, etc. You could say "the myth that women earn 7

Each of your sources says there is still a gender wage gap in the range of 5-9% after controlling for education, etc. You could say "the myth that women earn 77% of what men earn", but it is not correct to call the gender wage gap a myth.