The measurement of public opinion on abortion: the effects of survey design.

A factorial experiment examined the effects of the wording and sequence of survey questions on the measurement of attitudes toward abortion. When a first-trimester pregnancy is specified, 55% of respondents agree that a woman should be able to obtain a legal abortion for any reason, compared with 44% when no pregnancy duration is stated. Specifying first-trimester pregnancies has little effect on the proportion of respondents who agree that abortion should be available for maternal health, fetal defects or rape, but it significantly increases the proportion who agree that a woman should be able to obtain an abortion if she is single, has financial constraints or wants no more children. When gestational lengths from one to six months are presented to respondents in ascending order, agreement that a woman should be able to obtain an abortion for any reason is lower for any given length of gestation than when pregnancy durations are presented in descending order. Forty-eight percent of respondents agree that abortion should be legal for any reason when that question is posed after a series of specific reasons; however, 60% do so when it is the first question in the sequence. The difference in agreement with abortion for any reason between Catholics and non-Baptist Protestants, and between Republicans and Democrats, is much smaller when the question is asked first than when it is presented last.