[Karellen]

OK. Do you have any reason to suspect that the people making their calculation didn't take that into account? Of all the things that will vary over time, including the distance between the Earth and Moon, do you really think they'd have missed the fact that the Earth's gravity varies with distance?

If you've got what you think is a more accurate number, and can show your working, I'm sure the wikipedia editors would be willing to take a look at it.