Although this research
has advanced our understanding of PSM in important
ways, this understanding is “contingent on the
methods, populations, situations and underlying
assumptions involved in the process by which [it] has
been acquired” (McGrath et al. 1982, 105). In other
words, what we know ultimately depends on how
we know it. Given that our current knowledge of
PSM has been derived primarily from cross-sectional
survey research, our understanding remains limited
in critical ways.