The base-rate of hitch-hiking success and its moderators: A meta-analysis

- Hitch-hiking mode is derived from theory as a relevant construct.
- Gender is identified as a significant predictor of hitchhiking success.
- The base-rate of hitch-hiking success is computed.
- This is useful for calculating the necessary sample size for future research.

The inefficient use of automobiles has long become dissonance-provoking for ecologists and financially disadvantaged travellers. Although there are now more than a dozen psychological studies examining hitch-hiking success this is the first meta-analytic summary of the base-rate of hitch-hiking and its moderators. Every study reporting sufficient data to calculate the proportion of cars stopping divided by the amount of cars in total was included regardless of the gender and age of the hitch-hiking confederates and drivers. A random effects approach was used to calculate study weights and resulted in an overall mean proportion of 9.00% (CI = [8.0, 11.0]). Hitch-hikers' gender and publication type were significant moderators while controlling for country and year. Females, 12.57% CI[10.33, 14.81], had a higher base-rate than males, 5.71% CI[4.49, 6.92], while published studies, 10.30 CI [8.49, 12,11], had a higher base-rate than unpublished studies, 4.56 [2.96, 6.16]. All of the results were stable in the face of Trim and Fill as well as a leave-one-out analysis. Future research should continue to research the factors influencing hitch-hiking success (e.g. hitch-hiking mode: either standing at the side of the road signaling by thumbg/sign or requesting a ride by asking the drivers) while considering the base-rate to compute the necessary sample size. In practice the base-rate provides hitch-hikers a reasonable estimate of their average success, potentially limiting superstitious mannerisms.