How the points are calculated, as used on some of the lists on this site.

For the tables based on points, the following formula is used:

( ( ChartSize +1 - Position ) / 100 ) + ( 2.718 ^ ( -Position / 2) ) * ( 0.9 + ( weeknumber / 52 ) / 10 )

An explanation of the formula:

( ChartSize +1 - Position ) / 100 )

- This reverses the chart position and divides it by 100 so we don't end up with large points when they're all added together.
- Therefore a #1 position in the top 40 get 0.40 points and a #40 position will get 0.01 points.

( 2.718 ^ ( -Position / 2) )

- This adds an extra few points to the top positions so they are weighted more.
- --- Therefore a #1 position gets an extra 0.61 points, a #2 gets 0.37, a #10 gets 0.007. After #10 these values become miniscule.

( 0.9 + ( weeknumber / 52 ) / 10 )

- The value worked out above is then multiplied by a number that increases as the year increases. This takes into account the larger sales at Christmas, and the smaller sales at the beginning of the year.
- This value increases as the year goes on, but is always around 1.

This PDF document shows the values given to each position when the chart is made up of 40, 75 and 100 positions.

This points system was first developed and used on UKMix

Amazon