the size of Yemen

"Well, it's a case of Wikipedia using bad sources – a very common occurrence indeed. Surely, other sources must have gotten it right?" So I looked into the most reliable source: the CIA World Factbook, which claimed that the size of Yemen is 527,968 km2. The same number can be found in the World Bank database, the United Nations website, as well as an old geography book that I found in my closet. But it still diverges from the Google Maps number. Why? I delved into previous editions of the CIA World Factbook and found the earliest editions where the number appeared – 1991, exactly a year after the unification of Yemen happened.

I looked into previous editions and found separate entries for North and South Yemen – with the first one being 195,000 km2, and the second one being 332,968 km2. Both numbers were summed up to form the total size of United Yemen. But were they correct? I plugged the borders used in the textbook into Google Earth, and to my surprise, I found out that none of them were correct – North Yemen only had 136,000 km2, and South Yemen was only 288,000 km2. There was no possibility of some minor border or rounding error. They were both wildly off. What was happening here?