diff --git a/lectures/commod_price.md b/lectures/commod_price.md index 63cc1090..efab8144 100644 --- a/lectures/commod_price.md +++ b/lectures/commod_price.md @@ -32,7 +32,7 @@ We will solve an equation where the price function is the unknown. This is harder than solving an equation for an unknown number, or vector. -The lecture will discuss one way to solve a *functional equation* (the equation where the unknown object is a function). +The lecture will discuss one way to solve a [functional equation](https://en.wikipedia.org/wiki/Functional_equation) (an equation where the unknown object is a function). For this lecture we need the `yfinance` library. @@ -133,12 +133,12 @@ $p_t$. The harvest of the commodity at time $t$ is $Z_t$. -We assume that the sequence $\{ Z_t \}_{t \geq 1}$ is {ref}`IID ` with common density function $\phi$, where $\phi$ is nonnegative. +We assume that the sequence $\{ Z_t \}_{t \geq 1}$ is IID with common density function $\phi$, where $\phi$ is nonnegative. Speculators can store the commodity between periods, with $I_t$ units purchased in the current period yielding $\alpha I_t$ units in the next. -In general, $\alpha$ is a factor. Here $\alpha \in (0,1)$ is a depreciation rate for the commodity. +Here the parameter $\alpha \in (0,1)$ is a depreciation rate for the commodity. For simplicity, the risk free interest rate is taken to be zero, so expected profit on purchasing $I_t$ units is @@ -219,6 +219,8 @@ How can we find an equilibrium? Our path of attack will be to seek a system of prices that depend only on the current state. +(Our solution method involves using an [ansatz](https://en.wikipedia.org/wiki/Ansatz), which is an educated guess --- in this case for the price function.) + In other words, we take a function $p$ on $S$ and set $p_t = p(X_t)$ for every $t$. Prices and quantities then follow @@ -234,8 +236,6 @@ conditions above. More precisely, we seek a $p$ such that [](eq:arbi) and [](eq:pmco) hold for the corresponding system [](eq:eosy). -To this end, we apply the idea of [**ansatz**](https://en.wikipedia.org/wiki/Ansatz) here by supposing that there exists a function $p^*$ on $S$ -satisfying $$ p^*(x) = \max