I have been in the workforce for 30 years of full-time employment, 19 of those years have been in Human Resources, and I have observed that the inequities arise not mostly on education, experience or hours of work; but simply on the assumption that if a woman is doing a job it must be worth less.
I will give you a real example. In one company I worked for the positions of mediator between Management and the Workers were held by men, and during this period the jobs were all assigned levels of 10 and 11. Most of these people were not University-educated but had risen through the ranks and assumed the position.
Over a period of time women began to request the opportunity to work in these positions, within a short period of this occurring the FULLY QUALIFIED level for the job became a Level 8. No facet of the work had changed (including the hours of work) yet the job was immediately assigned a lower status, therefore a lower rate of pay.
You can observe this same phenomenon in banks and other parts of the white collar workforce.
It just strikes me as ironic that a woman wrote this book!