The impact of seemingly minor methodological changes on estimates of travel and correcting bias.

Abstract

In 1998, evidence was provided suggesting that an apparent 15% decline in domestic travel estimated from the Canadian Travel Surveys (CTS) of 1994, 1996, and 1997 was possibly misleading. This decline could actually be the result of methodological changes in the survey rather than a change in travel behaviour. Here, realistic assumptions and a simple computational method are utilized to demonstrate that change in bias may account for the drop in estimated trips. The analysis depends on a trip recall salience scale. Use of this scale allows correction for an under-reporting bias arising from reduced trip recall rates for low-salience trips. When the 1996 and 1997 CTS data are corrected, estimates of change in total trips are near zero. This finding corresponds to perceptions within the tourism industry. The bias correction methodology is applicable to other large surveys involving recall of past behaviour in which multiple events are recalled.