The gender pay gap will not close until 2186
The foundation's annual "Global Gender Gap Report" found that the workplace gender gap is now larger than at any time since 2008 after a 2013 peak, and is not estimated to close until 2186.
Last year, that projection was 2133.
The index measures factors including workplace participation and educational attainment for men and women.
The UK was the twentieth most gender-equal country in the index, far below its ninth-place peak in 2006.
That is partly because of a change in the way income is measured, but also because of a decline in female British politicians, legislators, and senior managers. The data was gathered before Theresa May became Prime Minister, which would have had an impact on the index.
Further details released by the Office for National Statistics (ONS) on Wednesday reveal a lack of progress with gender parity in the UK. The gender pay gap - the difference between men's and women's full-time median hourly pay - is still over 9%. Take a look at this chart:
That shows that it fell from 9.6% in 2015 to 9.4% in 2016. The gap was 17.4% in 1997, when ONS began measuring it, but it has been moving only sluggishly towards parity in recent years.
The difference is due to three primary reasons, according to the ONS:
1. Women are more likely to work part-time than men - 41% compared to 12% of the working age population. Part-time workers earn a lower hourly rate than full-time workers.
2. Women tend to work in lower-skilled jobs, such as caring or admin, which offer lower salaries. Over 15% of women work in caring roles, for example. while just 3% of men do.
3. Women spend more time caring for their children. Take a look at this chart:
It shows that the differences in pay for full-time employees is relatively small, but dramatically increase in the 40- 49 age bracket, when many women have taken time out of work to care for children.
Trades Union Congress (TUC) general secretary Frances O'Grady said: "The full-time gender pay gap is closing at a snail's pace. At this rate, it will take decades for women to get paid the same as men."
"We need a labour market that works better for women. This means helping mums get back into well-paid jobs after they have kids, and encouraging dads to take on more caring responsibilities."
Conservative MP Margot James said: "I am particularly pleased the gender pay gap is closing, but there is still more to be done to make sure women are treated equally."