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TOPIC 6 Putting the Economy Together: A Review (Mostly) The Money Market (Market 1): Money Supply Nominal Money Supply (M s ) : Affected By the Fed Fed conducts monetary policy to increase Money Supply - Open Market Operations - Decrease the reserve ratio

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Putting the Economy Together:

A Review (Mostly)

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The Money Market (Market 1): Money Supply

Nominal Money Supply (Ms):

Affected By the Fed

Fed conducts monetary policy to increase Money Supply

- Open Market Operations

- Decrease the reserve ratio

- Decrease the Discount Rate

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Money Market: Money Demand

Our model for the demand for real money balances takes the following form

Md/P = Ld(Y, r + πe)


Md = demand for nominal money balances (demand for M1)

Ld = demand for liquidity function

P = aggregate price level (CPI or GDP deflator)

Y = real income (real GDP)

πe = expected inflation

i = nominal interest rate on non-money assets

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Money Market Equilibrium

Money Market



Md = Ld(Y,πe)


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Interest Rates and Output

There are two effects between interest rates and output.

1) The IS curve. As interest rates fall, Investment increases and Y increases.

r falling causes Y to increase (negative relationship - the IS curve)

2) The transaction motive for holding money (the monetary feedback mechanism). As Y increases, demand for money increases and r increases.

Y increasing causes r to increase (positive relationship - the LM curve)

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Market 2 (Goods Market) - IS/LM

Y = Output = Aggregate Supply (optimizing firm behavior)

Y = Expenditures = C + I + G + NX = Goods Demand

IS curve - a quick review…..

  • How does the demand side of the economy change when interest rates change?

  • As real interest rates increase, I falls (user cost of capital rises), Y falls.

  • The above is how we modeled investment (firms optimize - user cost)

  • C and G (and NX) do not change with interest rates (NX likely will, but we will defer that for now). So, as r changes, total demand in the economy will increase.

  • In {Y, r} space, the demand for output slopes downward - we call this the IS curve.

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IS - Curve

IS Curve = Y = C + I + G + NX



I = f(r); C and G are not

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Investment/Savings (IS)


Snational = I + NX


Sprivate + (T - G - Tr) = I + NX

The IS Curve basically says that the investment in the economy must equal the savings.

A fall in r today (all else equal), will cause I to increase, which will cause Y to increase.

An increase in Y today (all else equal - including holding future Y constant), will cause S(private) to increase today - causing r to fall.

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What Shifts the IS curve (review)?

Things that will shift the IS curve to the Right

  • Through higher C demand:

    • higher Af

    • higher PVLR (including wealth effects)

    • higher Tr or lower T (holding ts fixed)

    • consumer confidence

  • Through higher I demand:

    • higher Af

    • lower tK

    • business confidence

      (not interest rate changes, that moves us along the curve)

  • Through higher G demand: higher G

  • Through higher NX demand: Higher foreign Y (eventually exchange rates).

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The LM (Liquidity-Money) Curve

LM Curve: (drawn in (Y-r) space) - represents the relationship of Y and r through the money market (specifically - Y’s affect on money demand).

The LM Curve relates real interest rates to real changes in output in the money market.

As Y increases - Md shifts upwards - causing real interest rates to rise (increase in transactions demand increases the demand for money).

What shifts the LM curve?

Money: Increasing Money Supply increases M/P causing the LM curve to the right.

Prices: Increasing Prices causes real Money Balances to fall shifting LM curve to the left.

πe: Increasing expected inflation causes returns on bonds (assets other than money) to increase making it less attractive to hold cash. Causes LM curve to shift right!

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IS-LM Equilibrium

Y* = f(N*,K,A)


LM = f(M,P,πe)


IS = f(G,PVLR,taxes,Af)



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Understanding the IS-LM Equilibrium: M increasing

Suppose M increases….


LM = f(M0)

LM = f(M1)

M increases





IS = f(G)






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Understanding the IS-LM Equilibrium: G increasing

Suppose G increases….

Y* = f(N*,K,A)


LM = f(M,P,πe)

G increases






IS = f(G1)

IS = f(G0)





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Understanding the IS-LM Equilibrium: P decreasing

Suppose P decreases….


LM = f(P0)

LM = f(P1 < P0)

P decreases





IS = f(G)






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The Aggregate Demand Curve

You may not have realized it yet,but we just made an aggregated demand curve!

The AD curve is drawn in {Y,P} space. It represents how the demand side of the economy responds to a change in prices. On the previous slide, we just did this!

As P decreases (holding everything else fixed - including M), M/P will increase. As real money balances increase, interest rates will fall, Investment will rise and Y will rise.

Prices affect the demand side of the economy through interest rates (and consequently investment).

Changes in prices do not affect consumption (consumption is only affected by PVLR - or real wages - if wages change 1 for 1 with prices (W/P is constant), PVLR will not change.

The AD curve comes directly from the IS-LM equilibrium. So, in essence, the AD curve is a representation of BOTH the IS curve AND the LM curve.

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What Shifts the AD curve?

  • Remember - the AD curve represents the demand side of the economy: Y = C+I+G+NX

  • Anything that causes the IS curve to shift to the right, will cause the AD curve to shift to the right (both the IS curve and the AD curve represent the demand side of the economy):

  • Anything that causes the LM curve to shift to the right (except price changes) will cause the AD curve to shift to the right.

    Example: Nominal money (M) increases, r will fall, I will increase, AD will shift right.

    With changes in money:

    LM shifts right

    Move along the IS curve

    Interest rates fall

    I increases

    AD shifts right.

    A change in prices will cause the LM curve to shift - but, will cause a movement along the AD curve.

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Shifting the AD curve (an example)


G increases




Y0 Y1


  • Suppose prices are held fixed (at P0).

  • Suppose that G increases and the Fed does not change M.

  • This implies that M/P will not change (i.e., the LM curve is fixed).

  • An increase in G will shift out IS curve. This will cause Y to increase.

  • An increase in G will lead to an increase in Y, holding P fixed.

  • The AD curve will shift right!

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Market 3: The Supply Side (a review)

Labor Market Review:

Ns(PVLR,taxes,value of leisure,





What is set in this market: N* (and real wages).

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Some Definitions

In Short Run (N adjusts, but it need not be at N*, K is fixed!)

  • Nominal Wages are ‘Sticky’ (although firms can adjust prices).

  • W is fixed, but not W/P (because firms can adjust P)

  • K by definition is fixed!

    Because Wages are sticky in Short Run, the labor market can be in ‘disequilibrium’ - ie, labor demand need not equal labor supply (cyclical unemployment can occur).

    In Long Run (N adjusts to N*, K is fixed)

  • We will be at N* (labor market is in equilibrium), but capital still does not adjust. (K is fixed!)

    In Really Long Run (Growth - N adjusts to N* and K is not fixed!)

  • Capital can adjust, labor market is in equilibrium

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Aggregate Supply Curves in the Long Run (LRAS)

In the long run, the labor market clears! (We are at N*)

Define: LRAS (full employment level of output) gives the level of output Y* associated with N*:

Y* = A F(K, N*, Raw Materials). Note Slight Modification (inclusion of raw materials)

LRAS Curve is vertical at Y* - the potential level of GDP. Y* is the level of output generated when the economy produces N*. Also know as the FE (full employment) line.

(w/p)e = the real wage in labor market equilibrium

N* = hours worked in labor market equilibrium

What shifts the Long Run AS Curve: N* or A (by definition K is fixed in long run)

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Notes on the Potential Level of GDP (Y*)

The Equilibrium level of Y is not necessarily optimal: Tax distortions can mean Y* is lower than is economically efficient. Equilibrium just means balance between private costs and benefits (in this case to household supply of labor and firm demand for labor). At an equilibrium, there is no incentive for people to change their behavior.

The Equilibrium is not constant: Changes to A, K and N* change Y*, and hence shift the LRAS. Y* trends upward in most countries (because A and K and population grow over time - shifting out N*). Many economists believe its growth rate is fairly stable.

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The Long Run AS Curve


P, r



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The Aggregate Supply: Short Run 1

The Short Run Aggregate Supply Curve (the relationship between output and prices) in the short run is positive.

Firms, if they get a demand shock, may chose to produce more (at a given fixed nominal wage) to satisfy demand. To take advantage of the higher demand, firms may raise prices (optimally) which drives down W/P. The lower real wages causes firms to optimally hire more labor - causing output to increase.

NOTE: Nd has not shifted!!!!!!Firms decide to meet the increase in demand for their product by hiring more workers because of the lower real wage (as prices increase). In short run, firms remain on their labor demand curve, while workers are off their labor supply curve temporarily (workers have little bargaining power, options in the short run).

There is disequilibrium in the labor market!

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The Short Run AS Curve (SRAS) - The Intuition

1. Labor Demand Curve 4. Short Run Aggregate Supply



As prices increase,

W/P falls







3. 45 degree line

2. Production Function








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Aggregate Supply in the Short Run (Part 1)

Labor Market Review:







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Notes on AS in Short Run (Part 1)

If firms get a positive demand shock (demand for goods increase), firms will raise prices and keep labor costs fixes. This will reduce real wages causing firms to hire more labor and produce more.

The Short Run AS Curve Slopes Upwards Because and increase in prices reduces real wages and causes firms to higher more workers and consequently to produce more.

Consequence, N > N* and Y > Y* and U < U*

U = current unemployment rate

U* = Natural Rate of Unemployment (only frictional and structural, no cyclical unemployment)

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More Notes on AS in Short Run (Part 1)

What Shifts the SRAS curve?

SRAS = F(A, K, N, raw materials).

K is fixed

A is exogenous (ie, I tell you when changes)

raw materials is the new twist. Anything that effects the nominal price of raw materials will effect the quantity of raw materials purchased and will shift the short run AS. For every given labor and capital - if the price of raw materials get more expensive, firms will produce less (ie, oil prices).

Nominal wages will adjust between the short run and the long run - that will cause the SRAS to shift between the short run and the long run!

For our discussion - only input prices (nominal wages and nominal oil prices) and technology will shift the SRAS! Higher costs of production means SRAS will shift in!

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Notes on AS in the Instantaneous Time Period

Some Macro Economists (Keynes) had the notion that prices are fixed in the short run. It is costly to keep changing your prices when faced with every given shock. As a result, prices in the market tend to change slowly. Think about the price of milk at Dominicks. Macro conditions are changing all the time and the price of milk - over the last 1/2 year has been about $1.79 per quart.

In this case - firms keep prices and wages fixed and just meet demand by requiring workers to work a little harder sometimes and a little less hard during other times. This is how they meet changes in demand without changing prices.

In this case - the labor market isn’t really in equilibrium at all in the short run. Concept is called efficiency wages - pay workers a slight premium because they realize that sometimes they work real hard and others they do not.

In such a case - prices are fixed…….. SRAS is horizontal

We will work with both the upward sloping (short run) and the horizontal (instantaneous) SRAS curves.

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The Expenditure - Output Equilibrium (AD, AS)

Y* = f(N*,K,A)


SRAS(1) = f(input prices)


AD = f(G,PVLR,taxes,Yf,M,Πe)



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The Self Correcting Mechanism

When the economy is in long run disequilibrium (Y (short run) not equal Y*), the economy will naturally move towards Y*.

Reason: Labor market will eventually clear. The reason that Y does not equal Y* is because N does not equal N*. As soon as the labor market clears, we will be back at N*.

How does the labor market eventually clear? Workers will not continue to work off their labor demand supply for long periods of time.

When N > N*, workers will be working more than their desired amount and will require the firm to raise nominal wages (W) so as to compensate them for their additional effort. Doing so, will cause labor market to clear.

But, if W increases, the short run AS will shift in (the cost of production has increased).

The exact opposite will work when N < N*.

As the labor market starts to clear, the SRAS will adjust to bring us back to Y*.

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Let the Fun Begin!

Examples and rules - bring lots of extra pages - we are going to do lots of examples!

Why did the 1991 recession occur?

How about the 1975 recession occur?

How about the 1982 recession?

What if I wanted to run for president? Suppose I had control of the Money Supply - what could I do in the short run? What about the long run?

What did the tech boom in the 1990s do to the economy? Why did Greenspan ‘RAISE’ interest rates in 2000? What was he thinking?

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How I start these problems?

Start with short run effects!

1. I look at the Demand Side of the Economy

A. Did IS or LM change?

B. Did AD change

2. I, then, look at the Supply Side - Did SRAS change

I ignore the labor market in the short run.

The long run is all about the labor market. For the long run (and Y*) I figure out what happens in the labor market!

In the long run - we always end up at Y* and Y* is determined in the labor market (along with A).