Public Debt, Distortionary Taxation, and Monetary Policy

Since Leeper's (1991, Journal of Monetary Economics 27, 129-147) seminal paper, an extensive literature has argued that if fiscal policy is passive, that is, guarantees public debt stabilization irrespectively of the inflation path, monetary policy can independently be committed to inflation targeting. This can be pursued by following the Taylor principle, i.e., responding to upward perturbations in inflation with a more than one-for-one increase in the nominal interest rate. This paper considers an optimizing framework in which the government can only finance public expenditures by levying distortionary taxes. It is shown that households' participation constraints and Laffer-type effects may render passive fiscal policies unfeasible. For any given target inflation rate, there exists a threshold level of public debt beyond which monetary policy independence is no longer possible. In such circumstances, the dynamics of public debt can be controlled only by means of higher inflation tax revenues: inflation dynamics in line with the fiscal theory of the price level must take place in order for macroeconomic stability to be guaranteed. Otherwise, to preserve inflation control around the steady state by following the Taylor principle, monetary policy must target a higher inflation rate.Public Debt; Distortionary Taxation; Monetary and Fiscal Policy Rules.

Lead, Follow or Cooperate? Endogenous Timing & Cooperation in Symmetric Duopoly Games.

The aim of this paper is to extend Hamilton and Slutsky's (1990) endogenous timing game by including the possibility for players to cooperate. At an initial stage players are assumed to announce both their purpose to play early or late a given duopoly game as well as their intention to cooperate or not with their rival. The cooperation and timing formation rule is rather simple: when both players agree to cooperate and play with a given timing, they end up playing their actions coordinately and simultaneously. Otherwise, they play as singletons with the timing as prescribed by their own announcement. We check for the existence of a subgame perfect Nash equilibrium (in pure strategies) of such a cooperation-timing duopoly game. Two main results on the emergence of cooperation are provided. If players' actions in the symmetric duopoly game are strategic substitutes and there is no discount, cooperating early is a subgame perfect equilibrium of the extended timing-cooperation game. Conversely, cooperating late (at period two) represents an equilibrium when players' strategies are strategic complements. Other equilibria are also possible. Most importantly, our model shows that, in general, the success of cooperation is a¤ected by the endogenous timing of the game. Moreover, the slope of players' best-replies appears crucial both for the success of cooperation as well as for the players' choice of sequencing their market actions.Endogenous Timing, Cooperation

Inequality, bankruptcy and the macroeconomy

This thesis examines the determinants inequality and its effects on macroeconomic outcomes, and in particular the economic effects of bankruptcy law. The first two chapters are joint work with Jochen Mankart. In the first chapter, we examine the effects of Chapter 7 of the US bankruptcy law on entrepreneurs. Entrepreneurs are subject to production risk. They can borrow and if they fail they can default on their debt. We examine the optimal wealth exemption level and the optimal credit market exclusion duration in this environment. In the second chapter, we introduce secured credit, in addition to unsecured credit in a model that is similar to the one in the first chapter. Secured credit lowers the cost of a generous bankruptcy regime because agents who are rationed out of the unsecured credit market can still obtain secured credit. Therefore, the optimal exemption level is very high. In the third chapter, I estimate stochastic process for earnings of Italian individuals. I find that individual’s earnings present statistically significant heterogeneity both in levels and in growth rates that is determined before the beginning of economic activity. In the fourth chapter, I analyze the quantitative effects of introducing immediate debt discharge (fresh start) in the procedures of personal bankruptcy law on the saving and default decisions of Italian household. I find that introducing fresh start in the Italian bankruptcy law would worsen credit conditions, without almost any benefit in terms of better insurance. The fifth chapter is joint work with Emanuele Tarantino and Nicolas Serrano-Velarde. In this chapter we exploit the recent reform of bankruptcy law in Italy to analyze the effects of bankruptcy regulation on the cost of credit. We find that strengthening firms’ rights to renegotiate outstanding deals with creditors increased the costs of funding, while simplifying the procedure of liquidation decreased the costs of funding. In the sixth chapter, I show that credit market imperfections are not necessary to generate an individual poverty trap

CRITICAL ISSUES IN APPLIED SPORT BIOMECHANICS RESEARCH

Applied sport biomechanics represents one of the most challenging fields of biomechanics of human movement. High-speed sport movements require thorough biomechanical analysis to have a good understanding of the different aspects of the techniques especially when working with elite athletes. Through the presentation of some studies carried out at the Bioengineering Center of Milan over the last five years this paper outlines same critical issues in applied sport movement researches. In particular, we investigated the operational feasibility and the reliability of the resulting quantitative kinematics analysis of using free-floating video cameras with variable optics for field three-dimensional sport movement analysis. In other experiments the critical issue of accuracy and reliability of the biomechanical measures was studied

EVALUATION OF THE LOWER LIMBS MOTOR STRATEGIES DURING VERTICAL JUMPING

Vertical jump is a test widely adopted by tainers to evaluate some motor characterisitcs of the athletes. The performance index usually measured, is the maximum vertical displacement of the centre of mass from its position when the athlete is standing. Aim of this paper is the study of the vertical jump through the variables related with the mechanical contribution of the muscular groups acting on the three main joints of the lower limb. Subjects of the study were 9 professional football players belonging to AC Milan football club. The players performed series of vertical jumps using either the thrust of both the legs, or the thrust of only one leg.The co-ordinates of five anatomical landmarks of the lower limb together with the ground reaction forces, were detected simultaneously by the ELITE System, with a sample frequency of 100 Hz. A specially designed software was implemented to compute the performance index ( differential height of the jump), the net joints' moments and the powers. The results show the following:-the performance index (average=539+-45mm)of the jumps performed with the thrust of both the legs, confirms the high athletic level of the players. -When the players jump with the thrust of one leg the performance index decreases significantly ( average=366+-44mm),-the maximal moments exerted bz the joints muscles when only one limb acts, are significatively greater than the correspondent values computed during the action of both the limbs. This difference almost disappears when the powers data are considered. This result is in relation with the different angular velocities of joints' extension. - even if vertical jump is a simple test easy to perform, especailly by people with high motor skills, it is possible to identify mechanical and moter asymetries between the same muscular groups of the two legs and between the motor patterns adopted by subjects characterised by the same performance index. The method seems to be useful to monitor the effect on the motor mechanisms due to specific training procedure and the motor recovery of the athlete after injuries

EFFECT OF DIFFERENT HANDLEBAR HAND POSITIONS ON FAST BRAKE LEVER REACHING MOVEMENTS IN CYCLING

INTRODUCTION: The aim of the present study was to evaluate the effect of different kinds of handlebar hand positions on fast brake lever reaching movements. The assumption motivating this study was that riding positions that provide quick access to brake levers allow athletes to more easily manage the braking operation when they are forced to suddenly decrease bicycle speed or change direction to avoid an unexpected obstacle. METHODS: Three high-level road cyclists were the subjects of this study. Each athlete was tested while pedaling on his own racing bicycle mounted on a magnetic braked roller simulator. The bikes were equipped with a Cinelli Spinaci clipon handlebar. While pedaling, the athletes were asked to reach, as quickly as possible, the brake levers and try to brake the wheels’ rotation in the shortest possible time. Seven handlebar starting hand positions were predefined and investigated, including the placement of the hands on the clip-on handlebar. The subjects performed the braking actions in response to external stimuli (visual and acoustic) and were free to choose when to start the movement. For each of the experimental conditions, data for 10 trials were acquired. The ELITE motion analysis system was used at a sampling rate of 100 Hz to collect the 3-D kinematic variables of the right upper limb segments with respect to the handlebar and right brake lever frame. Five retro-reflective markers were glued on the subjects’ skin, and markers were located on sticks fixed to the right brake lever and to the handlebar. To account for bicycle movements, the measured coordinates were referred, by trigonometry, to a reference system whose origin was the handlebar marker. The time the rider took to reach the right brake lever was defined as the time from the first detectable movement of the marker fixed on the third finger of the right hand (distal end of the 2nd phalanx) until the first movement of the brake lever marker. The effect of the different handlebar hand positions on brake lever reaching times was analyzed with one-way ANOVA. The existence of significant differences between conditions was then tested using the Newman Keuls post hoc test. RESULTS: The results of the data analysis were as follows: • In each of the examined experimental conditions, the time the athletes took to reach the brake levers (lower than 300 ms) represented a small fraction of the total time necessary to stop a bicycle after an emergency signal was perceived. • Hand positions slightly affected the access time to the brake levers that, on the average, ranged from 150 ms to 280 ms. Lower values were measured when the hands were placed very close to the brake lever mounts. • Riding with the hands placed on the clip-on handlebar lead to brake lever reaching- times as high as those measured for other traditional positions with the hand placed on the top of the handlebar

A 3-D KINEMATIC STUDY OF TWO POPULAR FLEXIBILITY TESTS

INTRODUCTION. Flexibility is the intrinsic property of body tissues which determines the range of motion achievable without injury in a Joint or group of joints Goniometers are often used to measure the range of motion of the joints. These devices have been criticized and their reliability questioned.. Part of the problem is with the instruments and part with the procedure for using them. To deeply understand the phenomenon of flexibility more accurate, precise, multiaxial measurements are desirable By using an automatic motion analyzer (accuracy 1/3000 the field of view), it was the purpose of this study to perform a 3-D analysis of two popular flexibility tests When possible, the data were compared with those obtained by standard goniometers. METHODS Four recreational athletes (age range: 24-40 yr.) were the subjects of this study They were required to perform the sit and reach test and the passive single-straight-leg raising test. Both the tests are usually used as a test for hamstring tightness even if the sit and reach test combines back and hamstring flexibility Before the measurements the subjects warm-up by performing 10 minutes of slow jogging, and slow stretching movements Ten trials for each exercise were executed with one-minute rest period between trials. Kinematic data were recorded by means of an optoelectronic system (ELITE) with a sampling rate of 100 Hz. Markers were placed on: C7, T3, T6, T9, T12, L3, and S1 to mark the spine; sacroiliac spines, iliac crests, great trochanters, femoral condiles, malleola, and fifth metatarsal heads to mark the pelvis and the lower limbs; acromions, elbows and wrists to mark the arms. The position of the internaI joint centers of the hip, knee and ankle were estimated from the position of external landmarks using a special software which inputs were anthropometric and kinematic data. The back profile was modelled using a cubic spline. RESULTS. Mean and standard deviation values of the hip range of motion during the sit and reach and the straight-leg raising test are outlined in table 1 and 2, respectively. The results showed significant bilateral differences for most of the parameters examined suggesting that evaluative procedures requiring controlateral comparisons may be inaccurate. The dynamic examination of the sit and reach exercise revealed large intersubjects differences in the way to come to the full extended position evidentiating a different degree of spine mobility among the subjects The comparison with standard goniometer measurements showed differences up to 24 degrees in the hip range of motion CONCLUSION. In summary, the model presented in this work: gives a good representation of the subjects during all the phases of the flexibility tests; provides a direct quantification of the range of motion in degrees; allows the measurement of several joints and joint actions, the control of compensatory movements, and a permanent record of the trials

A PROCEDURE FOR QUANTITATIVE KINEMATIC ANALYSIS IN RUNNING ON TREADMILL

The purpose of this paper is to describe and test a method and a special developed software package capable of doing a complete 3-D kinematic analysis in treadmill running, including the assessment of kinematic asymmetries by a simultaneous right and left analysis. A pilot study using 8 recreational runners demonstrated that accurate and repeatable quantitative data can be collected and analyzed with the procedure. Comparison of specific kinematic data with literature studies revealed same significant difference in total joint range of motion. Some measurements and samples plots are also presented and discussed. The method and the user friendly software presented here seems to be an useful tool for scientists, trainers and athletes to assess and evaluate biomechanical data during running