I do not expect that you will ask question again since the last one in 2012-10-03.
Yet you raised a good question regarding the ranking mechanism of Yahoo! Knowledge+.
Your question here is why Joshua would supersede your first place on the English board last week, while from the captured screen below, we can see that both you and Joshua were awarded 4 best answers last week.
You mentioned Economics so I checked the Economics board. Joshua indeed got some best answers there but you got none there.
Therefore, maybe a reasonable guess is that the ranking system takes other consideration into account when there is a tie in the ranking within a particular board.
Personally I think the system is not that clever enough to display equal number for the same rank. There should be some programming algorithm behind which governs the rank under these circumstances.
Hope that you would not give up.
Keep the good attitude and give more quality responses in different boards.
2014-02-11 17:30:02 補充：
The graph is too large in scale above.
If you can view the graph in another window, you can see the number of best answers:
1. Joshua (4)
2. TOMING88 (4)
3. Jenkin (2)
4. Ling (2)
5. Gary (2)
6. cha****** (1)