Memory for Past Vote: Implications of a Study of Bias in Recall

For political scientists and pollsters the way the individual voted on previous occasions provides an important source of data. In the absence of longitudinal studies, recall of past vote tends to be taken as equivalent to actual vote cast. How accurate is such recall? How far does accuracy decrease with time, where recall concerns not one, but two, previous elections? How far do errors introduce a systematic bias in the conclusions drawn from such data?