>> I'd love to see how this is calculated <<
Impossible, it's done in the dark room with blindfolders on, so it's impossible to see...
Consider it a game of pin the tail on the Donkey in the dark...LOL...
Someone blindfolds another, they spin them in a circle, and the they attempt to post a stickly note (MMM..LOL..) on a PPI chart (IP..LOL..)and then they turn the lights on...
As long as they hit the chart, it's considered good news for the economy because the chart only has low numbers on it...
This is why it took 4 weeks to be released...
They kept missing the chart...LOL...