It's fair to say the denominations that have adopted "liberal" stances on issues like homosexuality, e.g., ECUSA and PCUSA, are the ones losing membership at a much faster rate than may be occurring with other denominations. Is it all because of their shift away from biblical Christianity? I don't know for sure that anyone has questioned all those who left, but as a member of a PCUSA church (for now), I can attest that the denomination's adoption of left-wing/nonbiblical stances has been a major factor in driving people away.