I always have difficulty understanding what people expect here. How can they expect companies not to reward the people that progress in their career while others interrupt their career?
Are we supposed to just unfairly give people the same salaries when one worked part time instead for 4 years?
One thought is that we could reframe the question (as e.g., Sweden has done) and work to increasing gender equality.
If the starting point is recognizing that people have kids and it takes time to care for them, and both parents have that right and obligation.
From there, one could devise policies that encourage BOTH men and women to take parental leave and invest in high-quality childcare for when that parental leave is over.
Are we supposed to just unfairly give people the same salaries when one worked part time instead for 4 years?
We're supposed to fairly reward two people the same for doing the same job. If you have more experience then you should have more responsibilities - that is what should increase your wage, not simply "time served".
There are almost no jobs where two people are doing exactly the same thing where experience doesn't matter. It's idiotic to think an employer would prefer someone with less experience to do a job, regardless of responsibilities. Because employers prefer experience, that is reflected in the market value of the employees.
I wasn't offering a prescription with my comment, just observing that the evidence suggests the gender wage gap is a Real Thing. But:
Are we supposed to just unfairly give people the same salaries when one worked part time instead for 4 years?
Let's dig into that a bit.
Suppose Bob and Agatha are both working full-time at the same company as, for the sake of example, sales engineers, and they're both making $100K. Agatha goes on maternity leave, and afterward the company agrees to keep her on as a part-time sales engineer, working 25 hours a week at $62.5K.
If, after four years, she and Bob both apply for full-time senior sales positions, is it "unfair" for Agatha to be offered the same salary as Bob?
Are we supposed to just unfairly give people the same salaries when one worked part time instead for 4 years?