BeeDeeDubbleU - 5:31 pm on Oct 1, 2012 (gmt 0)
The problem with this is that Google has traditionally relied on signals like this to rank sites. It was cumulative but with more weight on the EMD. They think they are now clever enough to rank sites properly without using the more obvious signals like this but the results would suggest that they are a bit off the mark as yet.
Try some searches for singular and plural, e.g. cars and car.