Re: why do some brands of microwave popcorn yield fewer unpopped kernels

Their are a few factors that dominate the issue -- first is the "actual" 
type of corn and how well it is dried -- this requires good reproducibility 
for consistency -- if there is too much biological variability or too much 
processing variability, few kernels will pop. To the extent that a company 
controls its supply of raw material, this can vary from company to company. 
The second issue is that of storage -- how is the popcorn stored. Obviously 
if it picks up moisture or loses moisture, the ability to pop will change. 
In a large mass of popcorn, those closer to open surfaces face a different 
environment than those towards more inner points. So this too can cause 
variation between brands and with success over time for a particular 
consumer.