This paper provides evidence that hours of work are heavily influenced by
the particular job which a person holds. The empirical work consists of a
comparison of the variance in the change in work hours across time intervals
containing a job change with the variance in the change in hours across time
periods when the job remains the same. To the extent that workers choose
hours and these hours choices are influenced by shifts in individual
preferences and resources, the variance in the time change of hours should not
depend upon whether the worker has switched jobs. The desire to reduce or
increase hours could be acted upon in the current job. On the other hand, if
hours are influenced by employer preferences or if job specific
characteristics dominate the labor supply decision, then hours changes should
be larger when persons change jobs than when they do not. Using the Panel
Study of Income Dynamics and the Quality of Employment Survey, we find that
hours changes are two to four times more variable across jobs than within
jobs. This result holds for both men and women, is obtained for weeks per
year, hours per week, and annual hours, and is not sensitive to the use of
controls for a set of job characteristics (including the wage) which might
influence the level of hours persons wish to supply.
The finding that the job has a large influence on work hours suggests
that much greater emphasis should be given to demand factors and to job
specific labor supply factors in future research on hours of work. The
overwhelming emphasis upon the wage and personal characteristics in
conventional labor supply analyses of work hours may in part be misplaced.