Well, after further study I am prepared to believe wikipedia (not a source I usually trust) because if you follow their explanation you get the correct results. The order of the result do not matter (it's different for ODIs because there are no series taken in to account). It also explains why BD only gained 20 points from drawing a Test in SL while loosing the series.


Find the series result

Award 1 point to a team for each win

Award 1/2 point to a team for each draw

Award 1 bonus point to the team winning the series

Award 1/2 bonus point to each team if the series is drawn

Convert the series result to actual ratings points

If the gap between the ratings of the two teams at the commencement of the series is less than 40 points, then the ratings points for each team equals:

(The team's own series result) multiplied by (50 points MORE than the opponent's rating) PLUS

(The opponent's series result) multiplied by (50 points LESS than the opponent's rating)


At the start of the series Zim had 263 points from 7 matches, a rating of 38 - BD had 20 from 18, a rating of one.

Series result: 1 win each, series drawn: 1,5 p. each:

for Zim: 1,5 x 51 (Zim series' points x BD rating of 1 + 50) + 1,5 x -49 (BD series' points x BD rating of 1 - 50) = 3 points gained -- overall Zim move from 263 to 266 points from 10 matches, a rating of 27

for BD: 1,5 x 88 + 1,5 x -12 = 114 points gained -- overall BD move to 134 points from 21 matches, a rating of 6

Due to BD's low initial rating our rating would only have improved by winning the series 2-0, even a 1-0 would have let to a slip in the ratings (from 38 to 36).

In 2011 it was different because BD still had their series win against the Windies counting towards the rankings.

What this means is: As fans of BD and Zim, two teams who play each other regularly, we are well advised to cheer the other's exploits against everybody else, because if we keep loosing to all and sundry we will never get just reward for beating or drawing with each other. :D