Do pollsters call cell phones?
No. It is illegal for them to do so. This fact means that people who have only a cell phone and no land line will be systematically excluded from polls. Since these people tend to be mostly young people, the pollsters intentionally overweight the 18-30 year olds to compensate for this effect, but as more people drop their landlines, it is becoming a serious issue. Here is a report on the issue and below is a graph taken from the report.
