She also knows full well just how many tools she would have to use to make good on that promise. The causes of the wage gap aren’t simple; they are myriad and interlocking. One is experience. Women are much more likely than men to leave the work force or reduce their hours, often to care for family members, especially beginning in their early 30s, and that’s when the gender wage gap starts to swell. They disrupt their careers and miss out on raises and promotions.

The problem stems from the lack of support in the United States for a parent who’s trying to balance work and child rearing, a job that still mostly falls to women. We don’t guarantee paid family leave, a benefit just 13 percent of private sector employees get, and child care costs remain high. But when women have paid leave and access to steady, reasonably priced child care, their wages benefit. Mr. Trump’s daughter Ivanka stood on the convention stage in Cleveland last week and pointed this out, although given that his campaign has paid men more than women it’s unclear whether Mr. Trump will follow through on his daughter’s pledge that he will focus on equal pay.

Men and women also end up in different industries and occupations, and the ones dominated by men pay more. Women still make less in every industry and nearly every job, of course, including the fields where men make up the bulk of the work force. And when women move into a previously male-dominated area, the pay drops. Still, pushing women into the areas that pay better while also trying to raise the pay of the jobs that women already hold is one way to start closing the gap.

Other elements Mrs. Clinton has to take into consideration: Women in unionized workplaces have smaller differences in pay, but unionization rates have been on a steady decline for some time. Women also make up roughly two-thirds of all minimum-wage workers, so their pay would benefit from an increase.