problem with duplication i have a list of cities and if we have a product line availble in those cities. Along with the cities populations.

my end goal is to show what % of the population in the USA that has access to our product lines.

the issue I am having is that if there are multiple products in those cities. it will count the population multiple times.

table looks like 

Part #-  City- Population

i have a switch statement in the query dividing up the part # into the 6 product lines, so i would hopefully be able find the coverage of the population for each product line. however, I am having the sae issue.  Even when I use a group by statement, there is an issue with the populations being double counted.

let me know if any of this doesnt make sense