What causes shifts in the IS or LM curves?

This post goes over the economics of the IS/LM model and the possible causes for shifts in the two lines.  It is important to remember the two equations for IS and LM, any that change in the included variables could cause a change in the graph:

The IS (Investment and savings equilibrium) equation:

Y = C(Y-T(Y))+I(r)+G+NX(Y)
  1. Y = national income or real GDP
  2. C(Y-T(Y)) = consumption or consumer spending which is a function of disposable income
  3. (Y-T(Y)) = disposable income which is equal to national income minus tax (which is a function of income)
  4. I(r) = Investment which is a function of the real interest rate
  5. G = Government spending/expenditures
  6. NX(Y) = Net exports, where imports depend on income (Y)

Possible shifts in the IS curve:

Change in Fiscal policy (G):
  1. The government can increase government spending (shifting IS right) or decrease government spending (shifting IS left).
  2. The government can increase taxes which lowers consumer spending (shifting IS left) or decrease taxes which increases consumer spending (shifting IS right).

Consumers can change their savings rate (C):
  1. If consumers decide to save more (marginal propensity to consume declines) then consumer spending declines and the IS curve shifts left.
  2. If consumers decide to save less (marginal propensity to consume rises) then consumer spending increases and the IS curve shifts right.

Change in exports (NX):
  1. If exports increase (due to currency depreciation) we will see the IS curve shift right.
  2. If exports decrease (due to currency appreciation) we will see the IS curve shift left.
  3. Note: Imports are endogenous in the model (they are a function of Y) so generally change in imports has no effect on the IS curve.  However, depending on your professor, a change in imports will have the opposite effect on the IS curve that exports has, so a decrease in imports shifts IS right, and an increase shifts IS left.

A change in private fixed investment (I)
  1. If consumers/firms feel more confident about the future, they may invest more regardless of the interest rate.  This will cause an increase in investment (IS shifts right).
  2. If consumers/firms feel less confident about the future, they may invest less regardless of the interest rate.  This will cause a decrease in investment (IS shifts left).

he LM (Liquidity preference and money supply equilibrium) equation:

M/P = L(i,Y)

  1. M/P = the real money supple where M is the actual amount of money in the economy and P is the overall price level
  2. L(i,Y) = the real demand for money which is a function of the interest rate (i) and national income (Y)

Possible shifts in the LM curve:

A change in money supply (M):
  1. If the central bank (or Federal Reserve) decides to increase the money supply (by buying t bills) then the LM curve shifts right.
  2. If the central bank (or Federal Reserve) decides to decrease the money supply (by selling t bills) then the LM curve shifts left.

A change in transaction technologies, ie credit cards (L):
  1. If improvement in the velocity of money occurs such that people require less money to conduct all of their transactions, the LM curve will shift right (because the opportunity cost of holding money goes down because there is now an alternative).

A change in the overall price level (P):
  1. If the price level rises, the LM curve shifts left.  This occurs because people need more money to pay the higher prices, but the higher resulting interest rates lower the demand for money.
  2. If the price level declines, the LM curve shifts right.  This occurs because people need less money to pay the lower prices, and the lower interest rates increase their demand for holding money.

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    Anonymous said...

    Wow,this has been very helpful :)

    caroline .w. mbugua said...

    Has really did me good

    Anonymous said...

    Thnx..a lot

    Anonymous said...

    Very helpful

    Anonymous said...

    Awsome and extremely helpful article.. Thanks for writing.

    Mahmud Anas on November 20, 2015 at 1:56 PM said...

    tnx :) really helpful

    Gaurav Arora on December 4, 2015 at 11:55 PM said...

    Slope Changes are not written ???

    RIjad on December 20, 2015 at 5:43 AM said...

    A life saver, especially before a monetary policy exam :)

    Anonymous said...

    So clear

    Unknown on April 24, 2016 at 4:11 AM said...

    what change occur to LM curve when money supply increase?

    Ahmed Rehman on May 10, 2016 at 11:54 AM said...

    LM will shift to right side if money supply increase and to left side if it is decrease

    John Ndungu on July 1, 2016 at 7:25 AM said...

    simple and clear

    jane mwangemi on July 21, 2016 at 10:35 AM said...

    Very help full,well done.u direct to the point, no complications. Thanks alot

    Anonymous said...

    Thank you!this was very helpful.I didn't have a good understanding on IS-LM model, but now I got it.Tomorrow I have Economic test.Now I feel confident.Thanks again!

    Anonymous said...

    Saved my life

    megha majumdar on May 30, 2017 at 10:33 PM said...

    Boon to us

    Unknown on August 31, 2017 at 1:09 AM said...


    Anonymous said...

    Thank you for the summary!

    Srinivasarao sahukari said...

    Exordinary and simple way analysis. It helps to me a lot

    Anonymous said...

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    malikadeel66 5good on March 30, 2018 at 11:21 AM said...

    That's really helpful for beginners

    jonny paperown on April 16, 2018 at 5:34 AM said...

    This is just the information I was looking for I'm new to the whole blogging thing and this question was one of the things that was holding me back on getting started thanks a ton.
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