The Women at Work reference, the oldest of the three, occurs in an editor's introduction. Unfortunately, the sum total of what it provides is this:

A world profile on women, using selected economic and social indicators, reveals that women constitute one half of the world population and one third of the official labour force; perform nearly two-thirds of work hours; but according to some estimates receive only one-tenth of the world income and possess less than one-hundredth of world property.

There is no information on the indicators used or their sources, or what is meant by "some estimates." That is where the trail goes cold—the oldest source, completely unsourced.

However, in 2007 Krishna Ahooja-Patel, the editor over whom's initials that editorial appeared, published a book called Development Has A Woman's Face: Insights from Within the U.N.. In that book she attributes the formula to herself, and offers an unsourced sketch of the methods used, "based on some available global data and others derived by use of fragmentary indicators at the time, in the late 1970s."

The figures used for the formula were: women were 33 percent of the world's formal workforce, and they were "only on the low income level in the pyramid of employment," where—even in those lowly jobs, based on data from "several countries"—they earned 10 percent to 30 percent less than men. Therefore, "one could assume that women's income is only one-third of the average income of men." Since they were one-third of the workforce, and earned one-third as much as men, their total income was .33 * .33, or 11 percent. (She rounded it down to 10 percent.) In short, a guess based on an extrapolation wrapped round an estimate.

What about the dramatic conclusion, that women "possess less than one-hundredth of world property"? She offers only this explanation: "if the average wage of women is so low, it can be assumed that they do not normally have any surplus to invest in reproducible or non-reproducible assets." Hence, less than 1 percent. That's it. In fact, she adds, "In reality the figure may be much lower."

Source? "Various UN Statistics."

Who knows?

These things are hard to measure, hard to know, and hard to explain. Setting aside the problem that the data didn't (and still don't, completely) exist to fill in the numbers in this famous sequence of facts—the first and perhaps greatest problem is that we can't easily define the concepts, which is part of the feminist problem. Even in 1970, how could women own only 1 percent of property, when most women were married and in many countries had at least some legal claim to their families' property? Similarly, what claim did women who worked in homes and fields have to their husbands' cash incomes? And what about socialist countries (which were a big deal back then), where a lot of payment was in the form of in-kind transfers, and where various forms of collective ownership were pervasive?