"Furthermore these numbers only reflect those who answered the survey."

This is a misleading and potentially dangerous remark which appears to reflect a lack of understanding of the science behind conducting surveys, not to mention, statistics.

@pnfullifidian actually this is stated quite clearly on the pew research home page. They themselves have concerns about the validity of their research for this reason.

@JimOnTwoWheels on the post that spawned this one, I did just that. In their findings, the researchers themselves raise this concern. The religion poll was conducted via phone, so only those who happened to answer the phone and cared to spend their time taking the survey were included.