I have no way of knowing such a thing, I don't recall any one or any teaching even suggesting such a number.
You have a number of souls that have started into a human form of existence that changes constantly.
There's those that skip the process I've been speaking of, which is quite high
Those that are processed which is still a strong number of folks. . . probably 65% of the general population or more.
Then there are those migrating souls that, according to certain traditions, come from other dimensions and/or planets and taking on human life
We're talking about millions of entities, not all of which are earthbound if we're to accept traditional views around the principle.
When it comes to those manifested on this planet you have to include a multitude of things as well as scenarios that include short-lived babies and children who die from an illness or accident as well as the adults. Some traditions claim that the soul entity does not take possession of the body until the first breath is taken yet, it does hover over the mother and womb throughout the last trimester. Because of this, the "child" if aborted either deliberately or due to incident, also has a karmic result that frequently fulfills the imbalance that entity needed when it comes to the one serving as the mother/parents & family. Needless to say, this gets complicated but is actually simple when you understand the accounting process.
Critics want to scream about the math; more people alive now than ever before so how can this be, etc. but most such detractors only know the rudimentary ideas around the philosophy and don't take ALL the factors into consideration, including the soul-evolution from mineral, to plant, to animal (and species transitions) finally to human and all that involves. It's a very long, drawn-out process that I barely understand and yet, I understand the concept enough to see the logic behind it and the fact that it makes far more sense than some old dude with a book who only gives those that kissed his glowing tukkis eternal life and all others are cast into a state of eternal damnation. . . can't buy it! Far too many good and spiritually minded people in the world who are far better Christians than his hypocritical butt sniffers tend to be (and the same goes with Islam, etc. )