@@ -37,7 +37,7 @@ tags: [hide-output]
3737
3838This lecture studies two consumers who have exactly the same
3939nonfinancial income process and who both conform to the linear-quadratic
40- permanent income of consumption smoothing model described in the
40+ permanent income of consumption smoothing model described in this
4141[ quantecon lecture] ( https://python-intro.quantecon.org/perm_income_cons.html ) .
4242
4343The two consumers have different information about
@@ -87,7 +87,7 @@ We compare behaviors of our two consumers as a way to learn about
8787This lecture can be regarded as an introduction to some of the ** invertibility** issues that take center stage in
8888the analysis of ** fiscal foresight** by Eric Leeper, Todd Walker, and Susan Yang {cite}` Leeper_Walker_Yang ` .
8989
90- ## Two Representations of the ** Same ** Nonfinancial Income Process
90+ ## Two Representations of One Nonfinancial Income Process
9191
9292Where $\beta \in (0,1)$, we study consequences of endowing a
9393consumer with one of the two alternative representations for the change
201201\sigma_a^2 = \sigma_\epsilon^2 + [ 1 + (\beta - \beta^{-1})^2 \sum_{j=0}^\infty \beta^{2j} ] = \beta^{-1} \sigma_\epsilon^2 .
202202$$
203203
204- ### Application of Kalman filter
204+ ## Application of Kalman filter
205205
206206We can also obtain representation {eq}` eqn_2 ` from representation {eq}` eqn_1 ` by using
207207the ** Kalman filter** .
@@ -240,7 +240,7 @@ and $\Sigma = (1-\beta^2) \sigma_\epsilon^2$.
240240We can also obtain these formulas via the classical filtering theory
241241described in {doc}` this lecture <classical_filtering> ` .
242242
243- ### News Shocks and Less Informative Shocks
243+ ## News Shocks and Less Informative Shocks
244244
245245Representation {eq}` eqn_1 ` is cast in terms of a ** news shock**
246246$\epsilon_ {t+1}$ that represents a shock to nonfinancial income
@@ -333,7 +333,7 @@ for representation {eq}`eqn_2` is
333333$d_a(\beta) = \frac{1 -\beta^2}{1 -\beta } = (1 + \beta)$, another
334334fact that will be important below.
335335
336- ### Representation of $\epsilon_t$ in Terms of Future $y$’s
336+ ## Representation of $\epsilon_t$ Shock in Terms of Future $y_t$
337337
338338Notice that reprentation {eq}` eqn_1 ` , namely, $y_ {t+1} - y_t = -\beta^{-1} \epsilon_t + \epsilon_ {t+1}$
339339implies the linear difference equation
360360Thus, $\epsilon_t$ contains ** exact** information about an
361361important linear combination of ** future** nonfinancial income.
362362
363- ### Representation in Terms of $a_t$ Shocks
363+ ## Representation in Terms of $a_t$ Shocks
364364
365365Next notice that representation {eq}` eqn_2 ` , namely, $y_ {t+1} - y_t = -
366366\beta a_t + a_ {t+1}$ implies the linear difference
384384E [ y_{t+1} | y^t ] = (1-\beta) \sum_{j=0}^\infty \beta^j y_{t-j}
385385$$
386386
387- ### Permanent Income Consumption-Smoothing Model
387+ ## Permanent Income Consumption-Smoothing Model
388388
389389When we computed optimal consumption-saving policies for the two
390390representations using formulas obtained with the difference equation
@@ -468,7 +468,7 @@ Equation Approach” in the [quantecon lecture](https://python-intro.quantecon.
468468
469469All the code that we shall use below is presented in that lecture.
470470
471- ### Computations
471+ ## Computations
472472
473473We shall use Python to form ** both** of the above two state-space
474474representations, using the following parameter values
@@ -792,7 +792,7 @@ plt.title("innovations representation")
792792plt.legend()
793793```
794794
795- ### Simulating the Income Process and Two Associated Shock Processes
795+ ## Simulating Income Process and Two Associated Shock Processes
796796
797797We now describe how we form a ** single** $\{ y_t\} _ {t=0}^T$ realization
798798that we will use to simulate the two different decision rules associated
@@ -828,7 +828,7 @@ The above steps implement the experiment of comparing decisions made by
828828two consumers having ** identical** incomes at each date but at each date
829829having ** different** information about their future incomes.
830830
831- ### Calculating Innovations in Another Way
831+ ## Calculating Innovations in Another Way
832832
833833Here we use formula {eq}` eqn_3 ` above to compute $a_ {t+1}$ as a function
834834of the history
850850We can verify that we recover the same $\{ a_t\} $ sequence
851851computed earlier.
852852
853- ### Another Invertibility Issue
853+ ## Another Invertibility Issue
854854
855855This {doc}` quantecon lecture <hs_invertibility_example> ` contains another example of a shock-invertibility issue that is endemic
856856to the LQ permanent income or consumption smoothing model.
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