  The light curves of 'hypernovae', i.e. very energetic supernovae with $E_{51}
\equiv E/10^{51}$ergs $\gsim 5-10$ are characterized at epochs of a few months
by a phase of linear decline. Classical, one-dimensional explosion models fail
to simultaneously reproduce the light curve near peak and at the linear decline
phase. The evolution of these light curves may however be explained by a simple
model consisting of two concentric components. The outer component is
responsible for the early part of the light curve and for the broad absorption
features observed in the early spectra of hypernovae, similar to the
one-dimensional models. In addition, a very dense inner component is added,
which reproduces the linear decline phase in the observed magnitude-versus-time
relation for SNe 1998bw, 1997ef, and 2002ap. This simple approach does contain
one of the main features of jet-driven, asymmetric explosion models, namely the
presence of a dense core. Although the total masses and energies derived with
the two-component model are similar to those obtained in previous studies which
also adopted spherical symmetry, this study suggests that the ejecta are
aspherical, and thus the real energies and masses may deviate from those
derived assuming spherical symmetry. The supernovae which were modeled are
divided into two groups, according to the prominence of the inner component:
the inner component of SN 1997ef is denser and more $^{56}$Ni-rich, relative to
the outer component, than the corresponding inner components of SNe 1998bw and
2002ap. These latter objects have a similar inner-to-outer component ratio,
although they have very different global values of mass and energy.
