This paper analyses the behaviour of real interest rates in the Spanish economy between 1990 and 2005. Since inflation-indexed bonds are not available, changes in implicit real interest rates are estimated using several approaches suggested by macroeconomic and financial theory. In particular, we employ equilibrium conditions of a representative agent under several specifications of preferences. Moreover, we exploit no-arbitrage conditions in securities markets. The evidence we report indicates that inflation uncertainty could account for a notable part of the observed decrease in nominal rates. Consequently, the actual real cost of financing might have decreased significantly less than what the course of ex-post real rates would suggest.

Key words: real interest rates, intertemporal marginal rate of substitution.
JEL classification: E43, G12.