The Theory of Planned Behaviour (TPB) has received considerable attention in the literature.
The present study is a quantitative integration and review of that research. From
a database of 185 independent studies published up to the end of 1997, the TPB accounted
for 27% and 39% of the variance in behaviour and intention, respectively. The perceived
behavioural control (PBC) construct accounted for significant amounts of variance
in intention and behaviour, independent of theory of reasoned action variables. When
behaviour measures were self-reports, the TPB accounted for 11% more of the variance
in behaviour than when behaviour measures were objective or observed (R2s = .31 and
.21, respectively). Attitude, subjective norm and PBC account for significantly more
of the variance in individuals' desires than intentions or self-predictions, but intentions
and self-predictions were better predictors of behaviour. The subjective norm construct
is generally found to be a weak predictor of intentions. This is partly attributable
to a combination of poor measurement and the need for expansion of the normative component.
The discussion focuses on ways in which current TPB research can be taken forward
in the light of the present review.