Calculating population density by neighbourhood

Discussion created by m.cain on Dec 5, 2010
Latest reply on Dec 6, 2010 by m.cain

I have a population density raster (pop per square km on 10m grid cells) and a neighbourhoods polygon shapefile. I want to know the population by each neighbourhood (as a field in the neighbourhood table).

There were two ways I could think of doing this:
1. I use Zonal Statistics as Table and join the output table to the neighbourhoods shapefile

2. I convert the density raster to a points shapefile and then do a count by location or some such.

Either way though, I would assume that I would use the Sum field to determine the total population per neighbourhood. The sums appearing in the table though are phenomenally large and unrealistic (i.e., hundreds of millions of people per neighbourhood). Why is it that I need to divide this amount by 10,000 to get the more realistic value?