I think you missed the bit of the article where i quote figures for intersex. Good estimates seem to lie in the range of 2% to 4% of the population.
Issues lie around definition and recording of such: for a very long time, medics have tended to erase any mention of intersex by shoe-horning those individuals with intersex characteristics into existing gender categories. In some instances, they have intervened by advising surgery on children as young as 1 or 2.
That has changed drastically over the last few years. First, while the US still opts for early intervention, the UK position tends to be no surgical intervention unless medically (not socially) necessary until the individual is old enough to decide for themselves.
As for what gets defined as intersex...figures from ISNA have instantly recognisable gender variation at birth at somewhere between 1 in 1,000 and 1 in 2,000 (which is low, but still a lot higher than your figure).
However, they also add that there are other conditions that need to be taken into account (such as late developing adrenal hyperplasia) which very quickly shift the medical definition of intersex up to somewhere in the region of 2% to 3%. Add in karotype variation and you are closer to 4% (a figure quoted often by OII)...and if you also add social definitions, then 4% to 6% is not unrealistic.
In terms of medical/biological definitions of intersex, the vast majority of those who could fall within the definition will quite possibly never know unless affected by an illness that is co-morbid with an intersex variation - or are tested at the chromosomal level.
That means...think carefully about this...that a fair number of those posting may well be intersex without realising that they are....