  The integrated galactic initial mass function (IGIMF) is computed from the
combination of the stellar initial mass function (IMF) and the embedded cluster
mass function, described by a power law with index beta. The result of the
combination is a time-varying IMF which depends on the star formation rate. We
applied the IGIMF formalism to a chemical evolution model for the solar
neighbourhood and compared the results obtained by assuming three possible
values for beta with the ones obtained by means of a standard, well-tested,
constant IMF. In general, a lower absolute value of beta implies a flatter
IGIMF, hence a larger number of massive stars, higher Type Ia and II supernova
rates, higher mass ejection rates and higher [alpha/Fe] values at a given
metallicity. Our suggested fiducial value for beta is 2, since with this value
we can account for most of the local observables. We discuss our results in a
broader perspective, with some implications regarding the possible universality
of the IMF and the importance of the star formation threshold.
