Macroeconomics. Methodology and The Basic Two period Consumer Problem. Nicola Viegi. January 2017

Transcription

1 Macroeconomics Methodology and The Basic Two period Consumer Problem Nicola Viegi January 2017

2 What is This Course About? Economic Growth Unemployment Fiscal Policy Monetary Policy Crisis Learning to "Think" Macroeconomics.

3 Course Plan 1. The Methodology of Macroeconomics - Models and Reality 2. Some Fundamental Relationships - Trend and Cycle in the Macroeconomy 3. Economic Growth Theory and Growth Policies 4. Unemployment - The Long and the Short of t 5. Macroeconomics of the Short Run - Boom, Bust and Back 6. Fiscal Policy 7. Monetary Policy 8. Economic Crisis

4 How the Module Will Work Lecture notes and readings will be the main course material. There is no textbook. Available at Additional readings: all linked on the website. Assessment: Coursework 60% (Tutorials, Essay, Class Presentations, Class Workshops), Final Exam 40%. Contacting me: Room 2.05, best way to see me - send me an (nicola.viegi@up.ac.za) Mostly the course is not too technical, but will use algebra when can (better than English!)

5 Keeping up with current events and economic analysis Essential for your professional development News Comments and Research nstitutions

6 First: Some Methodology why we do what we do

7 ..n a Nutshell Economics is a science of thinking in terms of models joined to the art of choosing models which are relevant... Keynes (1938) "God put macroeconomists on earth not to propose and test elegant theories but to solve practical problems" Mankiw (2006)

8 Why Models?

9 Argument Models are key to the scienti c nature of economics understand complex social reality by laying bare a very large variety of causal relationships, one at a time Economics advances not by settling on the model, but by generating useful collection of models an inventory of partial explanations non-universality and context-speci city Models do not require math, in principle any causal statement contains an implicit model n practice, math often useful to clarify (and make explicit) the nature of assumptions, relationships, conclusions ensure conclusions follow logically from assumptions economists use math not because they are smart, but because they recognize they are not smart enough

10 How to gure out the relevant model the craft of economics Verify critical assumptions Which assumption really matter for the functionning of the model? Are other details of reality not considered in the model mportant to understand the mechanism we want to describe? Verify mechanisms e.g. do rms behave in posited way? e.g. does exchange rate respond to capital in ows? Verify direct implications e.g. does employment really respond negatively to (exogenous) increases in wages? e.g. does investment rise with capital-account liberalization? Verify incidental implications (comparative statics) e.g., do rms pass on cost increases in full? e.g., does investment respond to exogenous ows from abroad (aid, remittances)?

11

12

13 A First Model: ntertemporal Approach to Current Account Problem: South Africa Has a Persistent Current Account De cit How do we model the problem?

14 A First Model: ntertemporal Approach to Current Account Basic Current Account Relation: CA = (S ) + (T G ) Reasons for Current Account De cit: High consumption: perhaps temporary fall in output. High nvestment - sustainable if produces higher income in the future High government spending (or fall in taxes) - twin de cit hypothesis Private Sector s ntertemporal Choices Determine (S ) Government ntertemporal Choices Determine (T G ) Expectations of future events play an important role

15 A Two Periods Model Assumptions Two periods, Small Open Economy - World Ends after period T ncome is Manna from Heaven Consumer can Borrow or Lend in nternational Capital Market Consumer Not Permitted to Die in Debt nterest rate and Subjective Discount Rate Constants Representative Agent (one person per country) No Uncertainty

16 A Two Periods Model Consumer Problem max U (C 1, C 2 ) = u (C 1 ) + βu (C 2 ) subjected to the following budget constraint C 1 = Y 1 S 1 which reduces to the following: C 2 = Y 2 + (1 + r)s 1 C 1 + C r = Y 1 + Y r

17 Solution Using Lagrange Multiplier L (C 1, C 2, λ) = u (C 1 ) + βu (C 2 ) + λ Y 1 + Y r First Order Conditions: C 2 C r From which L C 1 = u 0 (C 1 ) λ = 0 L = βu 0 (C 2 ) C 2 L = Y 1 + Y 2 C r λ 1 + r = 0 C 1 C r = 0 L C 1 L C 2 = u 0 (C 1 ) βu 0 (C 2 ) = λ λ 1+r u 0 (C 1 ) 0 = β (1 + r)

18 First mplications of the model Assuming u 0 > 0 and u 00 < 0, this result implies: if r increases, u 0 (C 1 ) must increase relative to u 0 (C 2 ) - C 1 must fall relative to C 2 An increase in impatience, a reduction in β, produces the opposite result if β = (1 + r) 1, u 0 (C 1 ) = u 0 (C 2 ), hence C 1 = C 2 - Consumer tends to smooth consumption Substituting this last result in the budget constraint we have: C 1 = C 2 = (1 + r) Y 1 + Y r

19 De ning the Current Account Consumer tends to smooth consumption - but income is exogenous. nternational borrowing and lending to move income intertemporally First period CA 1 = Y 1 C 1 = B 2 Second Period CA 2 = Y 2 + rb 2 C 2 CA 2 = Y 2 + r (Y 1 C 1 ) C 2 CA 2 = (Y 1 C 1 ) = CA 1 mplications: if a country run a current account de cit, it is infact borrowing from abroad A country in current account de cit in period one need to have a current account surplus in the future to pay back the borrowing in period one

20 Adding Government (Balance Budget) G 1 = T 1, G 2 = T 2 C 1 + C r = Y 1 G 1 + Y 2 G r CA 1 = Y 1 + rb 1 C 1 G 1 = B 2 B 1 How does the presence of the Government a ect private consumption? C 1 = C 2 = (1 + r) (Y 1 G 1 ) + (Y 2 G 2 ) 2 + r for any Y and G (if β = (1 + r) 1 )

21 Temporary increase in public expenditure (G 1 > 0, G 2 = 0) Private sector smoothing behaviour makes very important the distinction between temporarary and permanent changes, or shocks. C 1 = C 2 = (1 + r) (Y 1 G 1 ) + (Y 2 ) 2 + r if Y 1 = Y 2, in absence of scal expenditure, the curent account will be always in equilibrium. CA 1 = Y C 1 CA 1 = Y (1 + r) (Y G 1 ) + (Y ) 2 + r CA 1 = (1 + r) G 1 < 0 = 2 + r CA 2 Current Account De cit in the rst period, CA surplus in the second.

22 MACROECONOMC THEORY FOR THE LONG RUN (GROWTH THEORY AND NATURAL RATE THEORY) (Subsubsubsection head:) seeks to explain the underlying long run trends in macroeconomic aggregates and how these trends may be in uenced by structural economic policy Key assumptions in long run theory: all prices are fully adjusted expectations are correct there are no (recurrent) exogenous shocks Taken together, these as if assumptions imply that employment is at its natural rate, that economic activity is determined solely from the economy s supply side, and that the economy evolves smoothly over time.

23 MACROECONOMC THEORY FOR THE SHORT RUN (BUSNESS CYCLE THEORY) seeks to explain the short-run uctuations in macroeconomic aggregates around the long run trends and how these uctuations may be dampened by macroeconomic stabilization policy Key assumptions in short run theory: Exogenous (stochastic) shocks to demand and supply Nominal rigidities Expectational errors These assumptions imply that output and employment may (and generally do) deviate from their natural rates and that economic activity is determined by aggregate demand as well as by aggregate supply

24 South Africa Real GDP Trend and Cycle RGDP Trend Cycle

25 Next Time - Economic Growth READ Easterly "The Elusive Quest for Growth" Chapters 1 and 2