MrsR, forgive for quoting amost the entire article, but it does answer many of your questions:-
men currently earn an average of £42,441 compared to £31, 895 for women doing the same jobs
The overall pay gap between men and women in this country is around 21 per cent, which means the new research confirms a previously noticed trend; the pay gap tends to be wider for women with higher educational qualifications.
^a gender pay gap exists in most developed countries, including Scandinavia and the US. The American research, carried out by the Census Bureau in 2007, is especially interesting because the country has had its own Equal Pay Act since 1963 but inequality persists right across the economy.
Female workers earned less than men in 20 industries and 25 occupation groups, and that was true even in sectors dominated by women; female secretaries earned 83.4 per cent of the salary paid to their male counterparts.
In traditionally male occupations such as lorry driving, women fared even worse, earning only 76.5 per cent of the weekly wage enjoyed by men. ^
in 2008 the American academics, sociologist Kristen Schilt and economist Matthew Wiswall, carried out a unique piece of research on people who had changed sex.
They cited the case of an economics professor, Donald McCloskey, who announced to his colleagues that he was having an operation to become Deidre; McCloskey was jokingly told by his head of department that it would mean a pay cut, but Schilt and Wiswall discovered that's the actual experience of many male-to-female transgender people.
Men who had surgery to become women earned 32 per cent less on average after the change, even after taking into account variables such as educational qualifications; women who became men earned 1.5 per cent more. The academics observed that becoming female often brings with it a loss of authority, harassment and a loss of employment, while becoming male tends to produce an increase in respect and authority.
The printed article gave even more examples of gender disparity for specific jobs, such as same-level executives in the same corproration, shop-floor workers in the same factory, and more. Interestingly, the shop-floor workers' pay gap was less than the executives and professors: Smith related this back to the fact of the equal pay movement having been driven by factory workers.