We consider a discrete-time pure exchange economy along the lines of Lucas (1982). Let
time t run from 0 to T. There is a finite number of trading dates, but one can also look at
the infinite-horizon version of our economy by adding an appropriate transversality condition
and taking the limit as T → ∞. There are two countries in the world: Home and Foreign.
Each country is endowed with a Lucas tree producing a country-specific perishable good. In
our baseline model, the uncertainty about the output of the trees is the only source of risk
in the economy. The state ωt
, an element of the set Ωt
, is the history of the economy up to
time t. This history occurs with probability π(t, ωt). In our notation hereafter, we suppress
the second argument, ωt
, unless necessary for clarity. The state-dependent outputs of the
Home and Foreign trees are denoted by Y (t) and Y
∗
(t), respectively, and the corresponding
prices of the goods by p(t) and p
∗
(t). The terms of trade, T oT, are defined as the price of the
Home good relative to that of the Foreign good: T oT ≡ p/p∗
.
4 We fix the world numeraire
basket to contain α ∈ (0, 1) units of the Home good and (1-α) units of the Foreign good,
and normalize the price of this basket to be equal to unity.