  We point out that in the large field regime, the recently proposed
superconformal D-term inflation model coincides with the Starobinsky model. In
this regime, the inflaton field dominates over the Planck mass in the
gravitational kinetic term in the Jordan frame. Slow-roll inflation is realized
in the large field regime for sufficiently large gauge couplings. The
Starobinsky model generally emerges as an effective description of slow-roll
inflation if a Jordan frame exists where, for large inflaton field values, the
action is scale invariant and the ratio \hat {\lambda} of the inflaton
self-coupling and the nonminimal coupling to gravity is tiny. The
interpretation of this effective coupling is different in different models. In
superconformal D-term inflation it is determined by the scale of grand
unification, \hat {\lambda} ~ (\Lambda_{GUT}/M_P)^4.
