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update_ar1_example
update_ar1_example; no spelling error.
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longye-tian committed Jul 28, 2024
commit f0218871cd98e640504ba5a9a5ae10351fb60f04
11 changes: 9 additions & 2 deletions lectures/ar1_processes.md
Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,9 @@ where $a, b, c$ are scalar-valued parameters

(Equation {eq}`can_ar1` is sometimes called a **stochastic difference equation**.)

```{prf:example}
:label: ar1_ex_ar

For example, $X_t$ might be

* the log of labor income for a given household, or
Expand All @@ -70,6 +73,7 @@ of the previous value and an IID shock $W_{t+1}$.

(We use $t+1$ for the subscript of $W_{t+1}$ because this random variable is not
observed at time $t$.)
```

The specification {eq}`can_ar1` generates a time series $\{ X_t\}$ as soon as we
specify an initial condition $X_0$.
Expand Down Expand Up @@ -330,7 +334,10 @@ Notes:
* In {eq}`ar1_ergo`, convergence holds with probability one.
* The textbook by {cite}`MeynTweedie2009` is a classic reference on ergodicity.

For example, if we consider the identity function $h(x) = x$, we get
```{prf:example}
:label: ar1_ex_id

If we consider the identity function $h(x) = x$, we get

$$
\frac{1}{m} \sum_{t = 1}^m X_t \to
Expand All @@ -339,7 +346,7 @@ $$
$$

In other words, the time series sample mean converges to the mean of the stationary distribution.

```

Ergodicity is important for a range of reasons.

Expand Down