Overstating value change: question ordering in the postmaterial values index

In much of his research on intergenerational value change, Inglehart uses a four-item index to calculate levels of postmaterial and material value orientations. Latter waves of the World Values Surveys administer a 12-item values index in which the original four-item index is embedded. In some of his research, Inglehart compares values estimated from stand-alone and embedded indices. Using a split sample design, we administered two versions of the longer values index to national probability samples of Australian adults and detected question-ordering effects. Proportions of postmaterialists relative to materialists were inflated when the four-item index was embedded in the longer values index. Comparing estimates of postmaterial values from stand-alone indices with indices embedded in the longer values measure is an unreliable method of assessing change in value orientations, as it overestimates the magnitude of value change over time.