HANDLING DONT KNOW SURVEY RESPONSES - THE CASE OF THE SLOVENIAN PLEBISCITE

The critical step in the drive toward an independent Slovenia was the plebiscite held in December 1990, at which the citizens of Slovenia vo ted overwhelmingly in favor of a sovereign and independent state, The Slovenian Public Opinion (SPO) survey of November/December 1990 was us ed by the government of Slovenia to prepare for the plebiscite, Becaus e the plebiscite counted as ''YES voters'' only those voters who atten ded and voted for independence (nonvoters counted as ''NO voters''), ' 'Don't Know'' survey responses can be thought of as missing data-the t rue intention of the voter is unknown but must be either ''YES'' or '' NO.'' An analysis of the survey data under the missing-at-random assum ption for the missing responses provides remarkably accurate estimates of the eventual plebiscite outcome, substantially better than ad hoc methods and a nonignorable model that allow nonresponse to depend on t he intended vote.