Long-term investment with stochastic interest and inflation rates: The need for inflation-indexed bonds

We examine the long term investment problem, under stochastic interest and inflation rates and within financial market incompleteness. Four basic financial assets are available on the financial market: a money market account (the cash), a real consumption good, a financial stock index and a bond with constant maturity. In this incomplete framework, we provide the general solution of the expected utility maximization. We compute the monetary loss from not having access to an inflation-indexed bond, in order to be hedged against the inflation risk. We show that this latter one usually reaches high levels (more than 1% per year). Thus, the magnitude of such costs reaches those of management fees or transaction costs. They highlight the significant value of introducing inflation-indexed bonds in the financial markets.