I have, on occasion, used American National Election Studies (ANES) cumulative file to do over time comparisons. Roughly half of those times, I have found patterns that don’t make much sense. Only a small fraction of the times when the patterns didn’t make sense have I chosen to investigate the data more closely as a likely explanation for aberrant patterns. The following ‘finding’ is a result of such effort.
ANES cumulative file (1948–2004) carries a variety of indices. In creating some of the indices, it appears pre-election measures have been combined with post-election measures in some of the years. If that wasn’t enough, at least one of the times, the same index in some years has pre-election measure combined with the post-election measure, while using only post measures in other years. Here’s an example –
‘External Efficacy Index’ (VCF0648) is built out of two items –
Item 1: Public officials don’t care much what people like me think.
Item 2: People like me don’t have any say about what the government does
Item 2 is asked both pre and post-election in some cycles. In 1996, efficacy was built from
960568 (pre), 961244 (post)
[you can ID post-election wave questions through the following coding category – Inap, no Post IW]. Post version of 960568 is 961245
While in 2000 it is built out of – 001527 (post), 001528 (post)
I have alerted the ANES staff, and it is likely that the new iteration of the cumulative file will fix this particular issue.