I have no idea of the accuracy of any of this (how could I?) but this post from The Officers’ Club is definitely worth reading:
The reported differentials between the two head counts is staggering. The [Israeli-American] Team has found that -through grossly inflated birth rates, fertility rates, net-immigration, and even double counts- PA officials overestimated the number of Palestinians to the tune of 1.5 million people. That may not be a whole lot if we’re talking about China, but when you consider the fact that The Team estimated actual Arab numbers somewhere around 2.41 million people, the scope of the deception is made crystal clear.
It would be interesting to know if anyone out there has deeper knowledge of all this.