Public Debt Management in Brazil

This paper derives the optimal composition of the Brazilian public debt by looking at the relative impact of the risk and cost of alternative debt instruments on the probability of missing the stabilization target. This allows to price risk against the expected cost of debt service and thus to find the optimal combination along the trade off between cost and risk minimization. The optimal debt structure is a function of the expected return differentials between debt instruments, of the conditional variance of debt returns and of their covariances with output growth, inflation, exchange-rate depreciation and the Selic rate. We estimate the relevant covariances by: i) exploiting the daily survey of expectations; ii) simulating a small structural model of the Brazilian economy under different shocks; iii) estimating the unanticipated components of the relevant variables with forecasting regressions. The empirical evidence strongly supports the funding strategy of Brazilian Treasury in 2003 of relying heavily on fixed-rate LTN bonds. It also supports its recent decision to revitalize the market for price-indexed bonds with the new NTN-B program of IPCA indexation. Though decreasing, the exposure to exchange rate risk appears too large suggesting that more efforts should be made to reduce funding in foreign currencies.

How defensive were lending and aid to HIPC?

We investigate whether defensive lending and defensive granting motivated the transfer of resources by official donors to low income countries. We estimate a dynamic panel of 75 low-income IDA and IDA-Blend countries for the period 1982 to 2008, where the sample includes 41 HIPC and a control group of other 34 low- income countries. Our results point to no evidence of defensive lending as opposed to strong evidence of defensive granting. Both bilateral and multilateral donors reduce their loans as the debt they hold increases (where such “correction” is actually weaker in the case of multilateral loans to HIPC). Official donors provide more grants as multilateral debt increases where this effect is significant only for debt- ridden HIPC countries. This result is consistent with a substitution of grants for loans and the new approach to debt sustainability, but questions the efficiency and selectivity of the aid policy.debt relief, foreign aid, highly indebted poor countries.

Managing Debt Stability

This paper presents a simple model in which debt management stabilizes the debt-to-GDP ratio in face of shocks to real returns and output growth and thus supports fiscal restraint in ensuring sustainability. The optimal composition of public debt is derived by looking at the relative impact of the risk and cost of alternative debt instruments on the cost of missing the stabilization target. The optimal debt structure is a function of the expected return differentials between debt instruments, of the conditional variance of their returns and of the conditional covariances of their returns with output growth and inflation. We then explore how the relevant covariances and thus the optimal choice of debt instruments depend on the monetary regime and on Central Bank preferences for output stabilization, inflation control and interest-rate smoothing. Finally, we estimate the composition of public debt that would have supported debt stabilization in OECD countries over the last two decades. The empirical evidence suggests that the public debt should have a long maturity and a large share of it should be indexed to the price level.debt management, debt structure, debt stabilization, inflation indexation, interest rates

The Debt Burden and Debt Maturity

At low and moderate levels of government debt, there appears to be little relation between the level of debt and its maturity. But at high levels of debt, a strong inverse relation emerges. We start the paper by documenting this inverse relation for those OECD Countries which have reached very high levels of debt. We then provide a theory of the joint movements of debt and maturity which can explain both sets of facts. It is based on the idea that, at high levels of debt, the government may need to decrease the maturity of the debt as debt increases, in order to maintain the credibility of its anti-inflation stance.

How is the Debt Managed? Learning from Fiscal Stabilizations

This paper provides evidence on the behavior of public debt managers during fiscal stabilizations. Such episodes provide valuable information on the way debt instruments are chosen because they allow to overcome the problem that policymakers' expectations of interest rates are generally not observable. We find that governments increase the share of fixed-rate long-term debt denominated in the domestic currency the higher is the conditional volatility of short-term interest rates, the lower are long-term interest rates, and the stronger is the fall in long-term rates that follows the announcement of the stabilization program. By contrast, conventional measures of the relative cost of issuing long-term debt, such as the long-short interest-rate spread, are not significant. This evidence suggests that debt managers tend to prefer long to short maturity debt because they are concerned about the risk of refinancing at higher than expected interest rates. However, when long-term rates are high relative to their expectations, they issue short maturity debt to minimize borrowing costs.This paper provides evidence on the behavior of public debt managers during fiscal stabilizations. Such episodes provide valuable information on the way debt instruments are chosen because they allow to overcome the problem that policymakers' expectations of interest rates are generally not observable. We find that governments increase the share of fixed-rate long-term debt denominated in the domestic currency the higher is the conditional volatility of short-term interest rates, the lower are long-term interest rates, and the stronger is the fall in long-term rates that follows the announcement of the stabilization program. By contrast, conventional measures of the relative cost of issuing long-term debt, such as the long-short interest-rate spread, are not significant. This evidence suggests that debt managers tend to prefer long to short maturity debt because they are concerned about the risk of refinancing at higher than expected interest rates. However, when long-term rates are high relative to their expectations, they issue short maturity debt to minimize borrowing costs.Non-Refereed Working Papers / of national relevance onl

Managing the Public Debt in Fiscal Stabilizations: the Evidence

This paper provides evidence on the behavior of public debt managers during fiscal stabilizations in OECD countries over the last two decades. We find that debt maturity tends to lengthen the more credible is the program, the lower is the long-term interest rate and the higher is the volatility of short-term interest rates. We show that this debt issuing strategy is consistent with optimal debt management if information bewteen the government and private investors is asymmetric, as it is usually the case at the outset of a stabilization attempt when private investors may lack full confidence in the announced budget cuts.This paper provides evidence on the behavior of public debt managers during fiscal stabilizations in OECD countries over the last two decades. We find that debt maturity tends to lengthen the more credible is the program, the lower is the long-term interest rate and the higher is the volatility of short-term interest rates. We show that this debt issuing strategy is consistent with optimal debt management if information bewteen the government and private investors is asymmetric, as it is usually the case at the outset of a stabilization attempt when private investors may lack full confidence in the announced budget cuts.Non-Refereed Working Papers / of national relevance onl

Managing debt stability

This paper presents a simple model in which debt management stabilizes the debt-to-GDP ratio in face of shocks to real returns and output growth and thus supports fiscal restraint in ensuring sustainability. The optimal composition of public debt is derived by looking at the relative impact of the risk and cost of alternative debt instruments on the cost of missing the stabilization target. The optimal debt structure is a function of the expected return differentials between debt instruments, of the conditional variance of their returns and of the conditional covariances of their returns with output growth and inflation. We then explore how the relevant covariances and thus the optimal choice of debt instruments depend on the monetary regime and on Central Bank preferences for output stabilization, inflation control and interestrate smoothing. Finally, we estimate the composition of public debt that would have supported debt stabilization in OECD countries over the last two decades. The empirical evidence suggests that the public debt should have a long maturity and a large share of it should be indexed to the price level

A mixed integer linear programming model for optimal sovereign debt issuance

Copyright @ 2011, Elsevier. NOTICE: this is the author’s version of a work that was accepted for publication in the European Journal of Operational Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version is available at the link below.Governments borrow funds to finance the excess of cash payments or interest payments over receipts, usually by issuing fixed income debt and index-linked debt. The goal of this work is to propose a stochastic optimization-based approach to determine the composition of the portfolio issued over a series of government auctions for the fixed income debt, to minimize the cost of servicing debt while controlling risk and maintaining market liquidity. We show that this debt issuance problem can be modeled as a mixed integer linear programming problem with a receding horizon. The stochastic model for the interest rates is calibrated using a Kalman filter and the future interest rates are represented using a recombining trinomial lattice for the purpose of scenario-based optimization. The use of a latent factor interest rate model and a recombining lattice provides us with a realistic, yet very tractable scenario generator and allows us to do a multi-stage stochastic optimization involving integer variables on an ordinary desktop in a matter of seconds. This, in turn, facilitates frequent re-calibration of the interest rate model and re-optimization of the issuance throughout the budgetary year allows us to respond to the changes in the interest rate environment. We successfully demonstrate the utility of our approach by out-of-sample back-testing on the UK debt issuance data

The Contribution of -Synuclein Spreading to Parkinson’s Disease Synaptopathy

Synaptopathies are diseases with synapse defects as shared pathogenic features, encompassing neurodegenerative disorders such as Parkinson’s disease (PD). In sporadic PD, the most common age-related neurodegenerative movement disorder, nigrostriatal dopaminergic deficits are responsible for the onset of motor symptoms that have been related to -synuclein deposition at synaptic sites. Indeed, -synuclein accumulation can impair synaptic dopamine release and induces the death of nigrostriatal neurons. While in physiological conditions the protein can interact with and modulate synaptic vesicle proteins and membranes, numerous experimental evidences have confirmed that its pathological aggregation can compromise correct neuronal functioning. In addition, recent findings indicate that -synuclein pathology spreads into the brain and can affect the peripheral autonomic and somatic nervous system. Indeed, monomeric, oligomeric, and fibrillary -synuclein can move from cell to cell and can trigger the aggregation of the endogenous protein in recipient neurons. This novel “prion-like” behavior could further contribute to synaptic failure in PD and other synucleinopathies. This review describes the major findings supporting the occurrence of -synuclein pathology propagation in PD and discusses how this phenomenon could induce or contribute to synaptic injury and degeneration

Redistribution of DAT/α-synuclein complexes visualized by “in situ” proximity ligation assay in transgenic mice modelling early Parkinson’s disease

Alpha-synuclein, the major component of Lewy bodies, is thought to play a central role in the onset of synaptic dysfunctions in Parkinson's disease (PD). In particular, α-synuclein may affect dopaminergic neuron function as it interacts with a key protein modulating dopamine (DA) content at the synapse: the DA transporter (DAT). Indeed, recent evidence from our "in vitro" studies showed that α-synuclein aggregation decreases the expression and membrane trafficking of the DAT as the DAT is retained into α-synuclein-immunopositive inclusions. This notwithstanding, "in vivo" studies on PD animal models investigating whether DAT distribution is altered by the pathological overexpression and aggregation of α-synuclein are missing. By using the proximity ligation assay, a technique which allows the "in situ" visualization of protein-protein interactions, we studied the occurrence of alterations in the distribution of DAT/α-synuclein complexes in the SYN120 transgenic mouse model, showing insoluble α-synuclein aggregates into dopaminergic neurons of the nigrostriatal system, reduced striatal DA levels and an altered distribution of synaptic proteins in the striatum. We found that DAT/α-synuclein complexes were markedly redistributed in the striatum and substantia nigra of SYN120 mice. These alterations were accompanied by a significant increase of DAT striatal levels in transgenic animals when compared to wild type littermates. Our data indicate that, in the early pathogenesis of PD, α-synuclein acts as a fine modulator of the dopaminergic synapse by regulating the subcellular distribution of key proteins such as the DAT