Upload
others
View
1
Download
0
Embed Size (px)
Citation preview
Debt as Safe Asset:Mining the Bubble03.a. xx
Markus K. BrunnermeierSebastian Merkel
Yuliy SannikovPrinceton and Stanford
Virtual Finance Workshop2020-12-07
How much government debt can the market absorb? At what interest rate? Is there a limit, a βDebt Laffer Curveβ?What is the impact on inflation?When can governments run a deficit without ever pa-
ying back its debt, like a Ponzi scheme, and nevertheless individual citizensβ transversality conditions hold?What is a safe asset? What are its features? Retrading?Why is government debt a safe asset? When do you lose safe asset status?Why is there debt valuation puzzle for US, Japanese? How do we have to modify representative agent asset
pricing and the FTPL?2
Questions of our times
Valuating Government Debt Think of a representative agent holding all gov. debt His cash flow is primary surplus
β¬π‘π‘βπ‘π‘
= πΈπΈπ‘π‘ β«π‘π‘β πππ π πππ‘π‘
πππ π β πΊπΊπ π ππππ + πΈπΈπ‘π‘ (πππ‘π‘= SDF) β¦ but Japan primary surplus was negative for 50 out of 60 years Can surpluses be negative forever? Yes, if gov. debt is safe asset
How to rescue the FTPL? 3
Asset Price = E[PV(cash flows)] + E[PV(service flows)]dividends/interest convenience yield
4
Whatβs a Safe Asset?
Asset Price = E[PV(cash flows)] + E[PV(service flows)]dividends/interest convenience yield
5
Whatβs a Safe Asset?
0
CF
0
CF
0 0
CFCF
00
CFCF
BA
BA
Portfolio of
Safe asset
Cash flowasset
shocks
shocks
β¦
β¦
β¦
Asset Price = E[PV(cash flows)] + E[PV(service flows)]dividends/interest convenience yield
Value come from re-trading
7
Whatβs a Safe Asset?
0
CF
0
CF
0 0
CFCF
00
CFCF
BA
BA β¦
β¦
β¦
Asset Price = E[PV(cash flows)] + E[PV(service flows)]dividends/interest convenience yield
Value come from re-trading Insures by partially
completing markets
Can be βbubblyβ = fragile
8
Whatβs a Safe Asset?
0
CF
0
CF
0 0
CFCF
00
CFCF
BA
BA β¦
β¦
β¦
Asset Price = E[PV(cash flows)] + E[PV(service flows)]dividends/interest convenience yield
2 π½π½s π½π½ππππ > 0 π½π½π π ππ < 0
1. Good friend analogy (Brunnermeier Haddad, 2012) When one needs funds, one can sell at stable priceβ¦ since others buy Idiosyncratic shock: Partial insurance through retrading - low bid-ask spread Aggregate (volatility) shock: Appreciate in value β negative π½π½ = πππ½π½ππππ + (1 β ππ)π½π½π π ππ < 0
2. Safe Asset Tautology Safe asset is a bubble from aggregate perspective - fragility
Other service flows: collateral constraint, double-coincidence of wants 9
Safe Asset Pricing Equation, 2 π½π½ππ, Fragility
Model with Capital + Safe Asset Each heterogenous citizen Μπ€π€ β [0,1]
πΈπΈ β«0β ππβπππ‘π‘ log πππ‘π‘οΏ½ΜοΏ½π€ ππππ s.t.
Each citizen operates one firm Output π¦π¦π‘π‘οΏ½ΜοΏ½π€ = πππ‘π‘πππ‘π‘οΏ½ΜοΏ½π€
Physical capital πππ‘π‘οΏ½ΜοΏ½π€
πππππ‘π‘
οΏ½ΜοΏ½π€
πππ‘π‘οΏ½ΜοΏ½π€ = (Ξ¦ πππ‘π‘οΏ½ΜοΏ½π€ β πΏπΏ)ππππ + οΏ½πππ‘π‘ππ οΏ½πππ‘π‘οΏ½ΜοΏ½π€
Aggregate risk:οΏ½πππ‘π‘ , πππ‘π‘, βπ‘π‘ exogenous process with aggregate shock πππππ‘π‘
Financial Friction: Incomplete markets: citizens cannot trade claims on ππ οΏ½πππ‘π‘οΏ½ΜοΏ½π€
11
A LA L
A LA L
Gov. debtMoney
Net
wor
th
πππ‘π‘οΏ½ΜοΏ½π€πποΏ½ΜοΏ½π€
πππππ‘π‘οΏ½ΜοΏ½π€
πππ‘π‘οΏ½ΜοΏ½π€= β
πππ‘π‘οΏ½ΜοΏ½π€
πππ‘π‘οΏ½ΜοΏ½π€ππππ + πππππ‘π‘β¬ + 1 β πππ‘π‘οΏ½ΜοΏ½π€ πππππ‘π‘
πΎπΎ,οΏ½ΜοΏ½π€ πππ‘π‘οΏ½ΜοΏ½π€ β πππππ‘π‘β¬
Model with Capital + Safe Asset Each heterogenous citizen Μπ€π€ β [0,1]
πΈπΈ β«0β ππβπππ‘π‘ log πππ‘π‘οΏ½ΜοΏ½π€ ππππ s.t.
Each citizen operates one firm Output π¦π¦π‘π‘οΏ½ΜοΏ½π€ = πππ‘π‘πππ‘π‘οΏ½ΜοΏ½π€
Physical capital πππ‘π‘οΏ½ΜοΏ½π€
πππππ‘π‘
οΏ½ΜοΏ½π€
πππ‘π‘οΏ½ΜοΏ½π€ = (Ξ¦ πππ‘π‘οΏ½ΜοΏ½π€ β πΏπΏ)ππππ + οΏ½πππ‘π‘ππ οΏ½πππ‘π‘οΏ½ΜοΏ½π€
Aggregate risk:οΏ½πππ‘π‘ , πππ‘π‘, βπ‘π‘ exogenous process with aggregate shock πππππ‘π‘
Financial Friction: Incomplete markets: citizens cannot trade claims on ππ οΏ½πππ‘π‘οΏ½ΜοΏ½π€
12
A LA L
A LA L
Gov. debtMoney
Net
wor
th
πππ‘π‘οΏ½ΜοΏ½π€πποΏ½ΜοΏ½π€
πππππ‘π‘οΏ½ΜοΏ½π€
πππ‘π‘οΏ½ΜοΏ½π€= β
πππ‘π‘οΏ½ΜοΏ½π€
πππ‘π‘οΏ½ΜοΏ½π€ππππ + πππππ‘π‘β¬ + 1 β πππ‘π‘οΏ½ΜοΏ½π€ πππππ‘π‘
πΎπΎ,οΏ½ΜοΏ½π€ πππ‘π‘οΏ½ΜοΏ½π€ β πππππ‘π‘β¬
Taxes, Bond/Money Supply, Gov. Budget Government policy Instruments Government spending βπ‘π‘πΎπΎπ‘π‘ Proportional tax πππ‘π‘πππ‘π‘ on capital Nominal government debt supply
ππβ¬π‘π‘β¬π‘π‘
= πππ‘π‘β¬ππππ
Nominal interest rate πππ‘π‘ Government budget constraint (BC)
πππ‘π‘β¬ β πππ‘π‘οΏ½πππ‘π‘π΅π΅:=
β¬π‘π‘ + βπ‘π‘πΎπΎπ‘π‘ πππ‘π‘ β βπ‘π‘π π π‘π‘β
= 0
Assume here: Gov. chooses ππβ¬, ππ; while πππ‘π‘ adjusts to satisfy (BC) Goods market clearing:
πΆπΆπ‘π‘ + βπ‘π‘πΎπΎπ‘π‘ = πππ‘π‘ β πππ‘π‘ πΎπΎπ‘π‘ 13Let οΏ½πππ‘π‘: = πππ‘π‘ β βπ‘π‘
Primary surplus (per πΎπΎππ)
Real prices and returns πππ‘π‘πΎπΎπΎπΎπ‘π‘ value of physical capital
Return πππππ‘π‘πΎπΎ,οΏ½ΜοΏ½π€ = ππ(1βππ)βπππ‘π‘
οΏ½ΜοΏ½π€
πππ‘π‘πΎπΎ+ Ξ¦ πππ‘π‘οΏ½ΜοΏ½π€ β πΏπΏ + πππ‘π‘
πππΎπΎ ππππ + πππ‘π‘πππΎπΎπππππ‘π‘ + οΏ½πππ‘π‘ππ οΏ½πππ‘π‘οΏ½ΜοΏ½π€
πππ‘π‘π΅π΅πΎπΎπ‘π‘ real value of gov. debt β¬π‘π‘/βπ‘π‘ = πππ‘π‘π΅π΅πΎπΎπ‘π‘
Return πππππ‘π‘π΅π΅ = (ππ β πππ‘π‘β¬
βοΏ½πππ‘π‘β¬
+ Ξ¦ πππ‘π‘ β πΏπΏππ=
β πππ‘π‘πππ΅π΅)ππππ + πππ‘π‘
πππ΅π΅πππππ‘π‘
Μπ€π€βs dynamic trading strategy of gov. bond Inflow (outflow) from selling (buying) bond Reduces (increases) future payoffs
14
Dividend Yield Capital gains
β inflation
Optimal real investment rate πππ‘π‘: (Tobinβs q)
Optimal consumption: πππ‘π‘ = πππππ‘π‘
Optimal portfolio choice: 1 β πππ‘π‘ =πππ‘π‘βπππ‘π‘ /πππ‘π‘πΎπΎ+οΏ½πππ΅π΅
πΎπΎοΏ½πππ‘π‘2 = 1 β πππ‘π‘
15
Optimality and market clearings
Two Stationary Equilibria (for πΎπΎ0 = 1)
16
Gordon-Growth Formula Closed Form Solution
πππΎπΎ = 1βππ οΏ½ππβπππΈπΈ πππππΎπΎ /πππ‘π‘βππ
πππΎπΎ =ππ + οΏ½πππ΅π΅ 1 + πποΏ½ππππ + οΏ½πππ΅π΅ + ππ οΏ½ππππ
β¬β =
πππΈπΈ ππππππ /ππππ β ππ
+1 β ππ 2 οΏ½ππ2β¬β
πΈπΈ ππππππ /ππππ β πππππ΅π΅πΎπΎπ‘π‘ =
οΏ½ππ β ππ + οΏ½πππ΅π΅ 1 + πποΏ½ππ
ππ + οΏ½πππ΅π΅ + ππ οΏ½πππππΎπΎπ‘π‘
ππ = ππ ππ+οΏ½πππ΅π΅βοΏ½ππππ
ππ+οΏ½πππ΅π΅+πποΏ½ππππ
ππππππ = πππππππ΅π΅ + 1 β ππ πππππΎπΎ ππ time preference rateππ adjustment cost for investment rateοΏ½ΜοΏ½ππππ΅π΅ = πππππ΅π΅ β ππ bond issuance rate beyond interest rateοΏ½ππ = ππ β π€π€ part of TFP not spend on gov.)
Individual Perspective πππππ‘π‘οΏ½ΜοΏ½π€/πππ‘π‘οΏ½ΜοΏ½π€ = βπππ‘π‘ππππππ β πππ‘π‘πππππ‘π‘ β Μπππ‘π‘οΏ½ΜοΏ½π€ππ οΏ½πππ‘π‘οΏ½ΜοΏ½π€
Bond as part of a dynamic trading strategy Cash flow from selling (buying) after negative (positive) idiosyncratic shock Price βbond-partβ of portfolio Integrate over citizens weighted by net worth share πππ‘π‘ππ ππππ and ππππ are negatively correlated β depresses weighted SDF
(higher discount rate)
Aggregate Perspective ππ Μ πππ‘π‘/ Μ πππ‘π‘ = βπππ‘π‘ππππππ β πππ‘π‘πππππ‘π‘
Without aggregate risk Μ πππ‘π‘ = ππβπππππ‘π‘
Lower social discount rate + Bubble term 17
Safe Asset Valuation Equation: 2 Perspectives
Individual Perspective πππππ‘π‘οΏ½ΜοΏ½π€/πππ‘π‘οΏ½ΜοΏ½π€ = βπππ‘π‘ππππππ β πππ‘π‘πππππ‘π‘ β Μπππ‘π‘οΏ½ΜοΏ½π€ππ οΏ½πππ‘π‘οΏ½ΜοΏ½π€
Bond as part of a dynamic trading strategy Cash flow from selling (buying) after negative (positive) idiosyncratic shock Price βbond-partβ of portfolio Integrate over citizens weighted by net worth share πππ‘π‘ππ ππππ and ππππ are negatively correlated β depresses weighted SDF
(higher discount rate)
Aggregate Perspective ππ Μ πππ‘π‘/ Μ πππ‘π‘ = βπππ‘π‘ππππππ β πππ‘π‘πππππ‘π‘
Without aggregate risk Μ πππ‘π‘ = ππβπππππ‘π‘
Lower social discount rate + Bubble term 18
Safe Asset Valuation Equation: 2 Perspectives
βPartial insurance Serviceβ
β¬β =
πππΈπΈ ππππππ /ππππ β ππ
+1 β ππ 2 οΏ½ππ2β¬β
πΈπΈ ππππππ /ππππ β ππ
ππ + ππ = discount rate
πΈπΈ ππππππ /ππππ = ππππ + ππππ + Μππ οΏ½ππ
Individual Perspective πππππ‘π‘οΏ½ΜοΏ½π€/πππ‘π‘οΏ½ΜοΏ½π€ = βπππ‘π‘ππππππ β πππ‘π‘πππππ‘π‘ β Μπππ‘π‘οΏ½ΜοΏ½π€ππ οΏ½πππ‘π‘οΏ½ΜοΏ½π€
Bond as part of a dynamic trading strategy Cash flow from selling (buying) after negative (positive) idiosyncratic shock Price βbond-partβ of portfolio Integrate over citizens weighted by net worth share πππ‘π‘ππ ππππ and ππππ are negatively correlated β depresses weighted SDF
(higher discount rate)
Aggregate Perspective ππ Μ πππ‘π‘/ Μ πππ‘π‘ = βπππ‘π‘ππππππ β πππ‘π‘πππππ‘π‘
Without aggregate risk Μ πππ‘π‘ = ππβπππππ‘π‘
Lower social discount rate + Bubble term 19
Safe Asset Valuation Equation: 2 Perspectives
βPartial insurance Serviceβ
β¬β =
πππΈπΈ ππππππ /ππππ β ππ
+1 β ππ 2 οΏ½ππ2β¬β
πΈπΈ ππππππ /ππππ β ππ
Only for s>0β¬β =
ππππππ β ππ
ππ + ππ = discount rate
ππ β οΏ½ΜοΏ½ππ΅π΅ = discount rate
πΈπΈ ππππππ /ππππ = ππππ + ππππ + Μππ οΏ½ππ
ππππ + ππππ
Bubble/Ponzi Scheme and Transversality Gov. Debt is a Ponzi scheme/bubble (in aggregate perspective) Service flow β partial insurance to overcome market incompleteness
Why does transversality condition not rule out the bubble? Individual Perspective
High individual discount rate (low SDF) since net worth
limππββ
πΈπΈ πππππππποΏ½ΜοΏ½π€ = 0 Aggregate perspective
Low βsocialβ discount rate (high SDF)limππββ
πΈπΈ Μ πππππππποΏ½ΜοΏ½π€ > 0
20
ππππ versus ππ for different οΏ½ππβ¬
21
ππππ = Ξ¦ ππ β πΏπΏ=ππ
β οΏ½ππβ¬
ππ = 1ππ logππ+οΏ½ππβ¬ 1+ππππππ+οΏ½ππβ¬+πποΏ½ππππ
β πΏπΏ
bubbly
ππ = .27,β =ππ3
, πΏπΏ = .1,ππ = .02, οΏ½ππ = .25,ππ = 3 ,
οΏ½ππβ¬
When primary deficit forever ππ < 0 βππβΊ οΏ½ΜοΏ½ππ΅π΅ > 0? Japan? Higher issuance rate β higher inflation tax β lower real return β ππππ < ππ
Higher issuance rate, οΏ½ΜοΏ½ππ΅π΅ β higher inflation tax But real value of bonds, β¬β, declines β lower βtax baseβ
22
Debt Laffer Curve
Flight to Safety: Comparative static w.r.t. οΏ½ππ Flight to safety into bubbly gov. debt πππ΅π΅ rises (disinflation) πππΎπΎ falls and so does ππ and ππ
Similar withstochastic idiosyncratic volatility 23
Aggregate risk state variable: Stochastic idiosyncratic volatility: ππ log οΏ½πππ‘π‘ = βππ log
οΏ½πππ‘π‘οΏ½ππ0ππππ + πππ₯π₯πππππ‘π‘
Stochastic TFP: πππ‘π‘ = ππ( οΏ½πππ‘π‘) s.t.πΆπΆπΎπΎ
οΏ½πππ‘π‘ = πΌπΌ0 β πΌπΌ1 οΏ½πππ‘π‘ linear
Policy (surpluses decrease in οΏ½πππ‘π‘): οΏ½ΜοΏ½ππ‘π‘β¬ = βππ0 + ππ1 οΏ½πππ‘π‘ Individual perspective: 2 terms of valuation equation X - cash flow term around 0 X - safe asset service flow term
dominates
25
Countercyclical Safe Asset
π½π½π΅π΅,ππππ > 0 for cash flow term (primary surplus term)
π½π½π΅π΅,π π ππ < 0 for service flow term (due to risk sharing)
26
Countercyclical Safe Asset β 2 Betas
Bubbles can pop
Able to prop up the bubble/safe-asset status by (off-equilibrium) hiking taxes (fiscal space)
Market maker of last resort to secure low bid-ask spread 10 year US Treasury in March 2020
Competing safe asset Interest rate policy of competing central banks βleast ugly horseβ
27
Loss of Safe Asset Status
Asset Pricing Safe asset is different β provides service flow Risk sharing via precautionary saving and constant retrading 2 terms: cash flow + service flow Split depends on perspective (individual vs. aggregate) different discount rates 2 π½π½ππ
Flight to safety creates countercyclical Safe Asset Valuations negative π½π½
Bubble mining for government Negative primary surpluses for decades (like in Japan) But has its limits (unlike MMT)
Bubbles can pop: Loss of flight to safe asset status Fiscal capacity to fend off + Market maker of last resort
28
Conclusion
Debt as Safe Asset:οΏ½Mining the BubbleοΏ½03.a. xxοΏ½Questions of our timesValuating Government DebtWhatβs a Safe Asset?Whatβs a Safe Asset?Whatβs a Safe Asset?Whatβs a Safe Asset?Safe Asset Pricing Equation, 2 π½π , FragilityModel with Capital + Safe AssetModel with Capital + Safe AssetTaxes, Bond/Money Supply, Gov. BudgetReal prices and returnsOptimality and market clearingsTwo Stationary Equilibria (for πΎ 0 =1)Safe Asset Valuation Equation: 2 PerspectivesSafe Asset Valuation Equation: 2 PerspectivesSafe Asset Valuation Equation: 2 PerspectivesBubble/Ponzi Scheme and Transversality π π versus π for different π β¬ Debt Laffer CurveFlight to Safety: Comparative static w.r.t. π Countercyclical Safe AssetCountercyclical Safe Asset β 2 BetasLoss of Safe Asset StatusConclusion