Abstract
We study interactions between two policymakers, central bank and government, in managing public debt as the result of a two-stage game. In the first stage, the institutional regime is established. This determines the equilibrium solution for the second stage, in which a differential game is played between the two policymakers. It is shown that, if the policymakers can communicate before the game is played (multiple-equilibrium), coordination problems can be solved by using the concept of correlated equilibrium.
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Notes
A number of empirical studies support the proposition that central bank independence and low rates of inflation are correlated (see, e.g., Berger et al. 2001). However, it has also been argued (see, e.g., Hayo and Hefeker 2002) that this correlation does not indicate causality and that the reasons why central banks are made independent are related to legal, cultural, political and economic factors.
Seminal studies are those of Sargent and Wallace (1981), Tabellini (1986), Alesina and Tabellini (1987) and Turnovsky et al. (1988). More recent contributions are, among others, Levine and Brociner (1994), Neck and Dockner (1995), Pappa (2004). Particular emphasis has been recently placed on the problem of macroeconomic policy coordination in a monetary union (see, e.g., Cooper and Kempf 2000; Beetsma et al. 2001; Buti et al. 2001; Beetsma and Jensen 2004; van Aarle et al. 2002, 2004; Engwerda et al. 2002; Dixit and Lambertini 2003; Plasmans et al. 2005).
See North (1990) for a discussion of institutions as rules of the game.
Two-stage games have recently been used in order to establish the institutional arrangements (first stage) separately from the “main” game that is played in such arrangements (second stage). An example is provided by non-cooperative endogenous coalition theory: in the first stage coalitions are formed, whereas in the second stage coalitions play the game (Ray and Vohra 1999). van Aarle et al. (2002) provide an economic application of this approach to the coordination of fiscal and monetary policies in the EMU.
The private sector consists of small agents. They do not act strategically and therefore, their joint decisions on consumption and savings affect only the parameters of the model.
It can be a legislative device or an external authority which prevents the players from reneging on the announcements made, a reputation mechanism so that the player who deviates will not be believed in the future, or an institution which enhances the players’ credibility.
Notice that the central bank and the government have the same rate of time preference ρ (assumed to be constant over time) and the same time horizon, which is infinite.
Tabellini (1987) justifies the inclusion of public debt in the policymakers’ loss function by appealing to the fact that, in the absence of lump-sum taxes, a larger stock of public debt implies larger tax distortions in order to pay interest on the debt. Another reason for including the level of public debt among the central bank’s objectives is offered by the fiscal theory of the price level. According to this theory, if fiscal policy does not ensure satisfaction of the government’s inter-temporal budget constraint, then the price level must do so and the central bank cannot control inflation (see Woodford 2001, and literature cited therein). If doubts exist as to the independence of the central bank, further reasons for including public debt among monetary policy targets are the preoccupation with an inflation bail-out, were the central bank forced to give in to government pressure for monetizing the debt, or for an ex-post bail-out, in the case of a financial crisis stemming from the government defaulting on its debt.
The assumption that a is constant over time is introduced to limit the analytical complexity. An endogenous real interest rate would imply a non-linear dynamic constraint in the differential game. Similar assumptions are very common in the literature (see, among others, Tabellini 1986; Jensen 1994; van Aarle et al. 1995, 1997; Beetsma and Bovenberg 1997; Muscatelli et al. 2003).
Without loss of generality, we only consider the case in which F > M so that \( \bar d > 0 \).
Formally, this is due to the fact that, in all the regimes, deviations from instrumental variable targets equal the shadow prices of the fiscal debt for the policymakers (see Eqs. (6) and (7)).
“One can imagine a monetary authority sufficiently powerful vis-à-vis the fiscal authority that by the imposition of slower rates of growth of base money […] it can successfully constrain fiscal policy by telling the fiscal authority how much seigniorage it can expect. […] On the other hand, one can imagine that the monetary authority is not in a position to influence the government’s deficit path but is limited simply to managing the debt that is implied by the deficit path chosen by the fiscal authority. Under this second scheme the monetary authority is much less powerful than under the first scheme” (Sargent and Wallace 1981, p. 158).
The following results can be easily verified with standard calculus. Proofs are, however, available upon request.
The six rankings are obtained by combining the inequalities \( \bar V_{V} < \bar V_{W} \) and \( \bar V_{N} < \bar V_{G} \).
These are, together with their homologues for G, (recall that we have assumed the same ordering of the losses between the two policymakers): (1) \( \bar V_{N} < \bar V_{V} < \bar V_{G} < \bar V_{W} \), (2)\( \bar V_{N} < \bar V_{G} < \bar V_{V} < \bar V_{W} \), (3)\( \bar V_{V} < \bar V_{W} < \bar V_{N} < \bar V_{G} \), (4) \( \bar V_{V} < \bar V_{N} < \bar V_{G} < \bar V_{W} .\)
In our context the ranking \( \bar V_{N} < \bar V_{V} < \bar V_{W} < \bar V_{G} \) (together with its homologous ranking for G) describes a coordination game with common interest.
Since binding agreements in a non-cooperative game are ruled out by definition, only self-enforcing agreements have to be considered.
The Nash equilibrium in mixed strategies is \( \left[ {\begin{array}{*{20}c} {p^{\prime}} & {1 - p^{\prime}} \\ p & {1 - p} \\ \end{array} } \right] \). In this equilibrium the central bank must be indifferent between being leader or follower. This requires that the probability with which the government chooses to follow the leader, denoted by p, should be such that: \( V(f, \cdot ) = p\bar V_{N} + (1 - p)\bar V_{G} = p\bar V_{V} + (1 - p)\bar V_{W} = V(l, \cdot ) \) Analogously, the probability with which the central bank chooses to follow the leader, denoted by \( p^{\prime} \), should be such that: \( G( \cdot ,f) = p^{\prime}\bar G_{N} + (1 - p^{\prime})\bar G_{V} = \) \( p^{\prime}\bar G_{G} + (1 - p^{\prime})\bar G_{W} = G( \cdot ,l) \).
See, e.g., the discussion in Dixit (2000).
Which is of major importance to ensure the accountability of individual policy-makers.
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Acknowledgements
The authors would like to thank N. Acocella, F. Ambrosio, V. Di Simone, A. Hughes Hallett, P. Krusell, S. Papa and participants at the workshop on “Sustainability of Public Debt” in Klagenfurt for their comments. The usual disclaimer applies. This research project has been supported by MIUR (PRIN 2005) and a Marie Curie Transfer of Knowledge Fellowship of the European Community’s Sixth Framework Program under contract number MTKD-CT-014288. Giovanni Di Bartolomeo would also like to acknowledge the hospitality of the University of Crete.
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Di Bartolomeo, G., Di Gioacchino, D. Fiscal-monetary policy coordination and debt management: a two-stage analysis. Empirica 35, 433–448 (2008). https://doi.org/10.1007/s10663-008-9077-0
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DOI: https://doi.org/10.1007/s10663-008-9077-0