Surveying the Left - Right Dimension : The Choice of a

Although left-right items are a standard tool of public opinion research, there remains some difference of opinion on the optimal response format. Two disputes can be identified in the literature: (a) whether to provide respondents with a small or large number of answer categories and (b) whether or not to administer the response scale including a midpoint. This study evaluates the performance of the 101-, 11and 10-point left-right scales. These scales not only speak to the two disputed aspects of measuring the left-right dimension but are also common instruments in public opinion research. Drawing on data from a split ballot multitrait multi-method experiment carried out in a methodological pretest to the German Socio-Economic Panel (SOEP), the analysis shows that the choice of a response format makes a difference in terms of data quality: The 101and 10point scales are plagued by method effects. Moreover, an application from electoral research illustrates that the choice of response formats affects substantive interpretations about the nature of the left-right dimension. Since all three scales perform about equally well in terms of the ease of administration, the findings suggest that the 11-point left-right scale should be used in survey research.