NationStates Jolt Archive

I have seen references in posts to a GDP-Calculator. Can someone tell me what this is and how I access it please? If this question is answered elsewhere I apologise, but I have searched on variations of these terms, as well as the terms themselves, and not found anything. Nor have I found anything in the FAQ's.

Thanks for your help

The most popular one is Pipian, here (http://www.pipian.com/stuffforchat/gdpcalc.php).
Others include Esyn (http://www.esyn.org/SOTA/NationStates.html) and mine (http://members.fortunecity.com/thracetailteann/html/gnp.html).