I developed the site a number of years ago. It's a little out dated at the moment but all the data is correct and has been pulled from CSO, ESRI, NAMA and other official publications. Nothing is made up and all sources should be referenced. If there are errors then they're human errors on my part only and I'd be happy to fix them. I'm not a statistician or anything like that, I'm a web developer.
If you spot any errors or if you just have feedback in general then I'm always happy to take a look so feel free to contact me via the site.