One point is that the majority of "Afrikaners" (insofar as the term was being used) did not trek to the interior or to Natal. A second is that nobody really took a good census, so we've had to piece it together from the records that are available. According to Herman Giliomee, who is really the foremost authority on Afrikaner history, in the first wave of voortrekker movement, about 10% of the colony's white population moved out by 1840 (20% of the Eastern district population); by that time about six thousand people had trekked. Giliomee states that by 1845 "some 2,308 families, or fifteen thousand burghers and their families, accompanied by an estimated five thousand servants, had left the [Cape] colony" (both figures from The Afrikaners [2003, 1st. ed.], 161). He may be misspeaking in general terms when saying "burghers" there, because that word did not mean any white person, but only white males of majority age. He also bases his numbers there on J. C. Visagie's figures, which must be eyed warily, because that would require nine or ten thousand natrekkers to go inland between 1840 and 1845. But with Europeans and others moving into these areas as well, it was hard to pin down any numbers beyond what the commando leaders and trek parties themselves recorded; once they settled into republics, census-taking was not high on their list of priorities.