This research investigates the validity threat to the Technology Acceptance Model on account of the manner in which “use” has been operationalized in the empirical literature. A meta-analysis of the cumulative empirical evidence finds that the average correlation between “perceived usefulness” and “use” is 0.26 in studies employing behavioral measures of use and 0.56 in studies employing perceptual measures of use.
Sharma, Rajeev and Yetton, Phillip, "An Evaluation of a Major Validity Threat to the Technology Acceptance Model" (2001). ECIS 2001 Proceedings. 126.