Inconsistent PR and back links results

[tonyww]

Why is it that I have found examples where the combination of PR and backlinks does NOT determine the ranking order.

Here are the results for a random phrase I chose 'road traffic accident' in google.com. The first number it the PR and the second number the number of back-links

1st: PR6 - 26 links

2nd: PR8 - 498 links <--! why not 1st? It has higher PR and more links than the number 1 rank.

3rd: PR4 - 5 links

4th: PR4 - 5 links

5th: PR7 - 214 links <--! why not 3rd?

These results can be repeated for other search terms.

Does anyone know why this occurs?

Thanks, Tony