Subsequently, the impact of strategic and HR flexibility on productivity within each
of the four planning modes is explored. Interaction terms between flexibility and firm
category are therefore added to the ANCOVA model. Table 2 shows for each of the four
firm categories the expected productivity difference that high flexibility makes in
comparison with low flexibility, with high (low) flexibility being more than (less than or
equal to) the total sample mean on the flexibility scales. The results confirm the
expectation about the positive association between HR flexibility and the effectiveness of
the moderate top-down mechanism. However, since this negative association is also
present for moderate bottom-up planners, this does not confirm the proposition made in
previous research that in a context of low HR flexibility the bottom-up approach is a
better alternative than the top-down approach. Moreover, an additional comparison of the
effects of both vertical alignment approaches indicates that in case of a lack of HR
flexibility the bottom-up approach has no significant better impact on productivity than
the top-down approach.