  Traditionally, inflationary models are analyzed in terms of parameters such
as the scalar spectral index ns and the tensor to scalar ratio r, while dark
energy models are studied in terms of the equation of state parameter w.
Motivated by the fact that both deal with periods of accelerated expansion, we
study the evolution of w during inflation, in order to derive observational
constraints on its value during an earlier epoch likely dominated by a dynamic
form of dark energy. We find that the cosmic microwave background and
large-scale structure data is consistent with w_inflation=-1 and provides an
upper limit of 1+w <~ 0.02. Nonetheless, an exact de Sitter expansion with a
constant w=-1 is disfavored since this would result in ns=1.
