The top decile starts at 90% and goes up from there. How else would it work?

I think what wildeabandon means is that your poll contains no option which could sensibly be ticked by somebody who has an income of more than £946.80/week – you've got the "less than or equal to £946.80" option, followed immediately by the "no income in that sense".

eta: oh, now I see the comment where that's already been clarified, sorry.