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This doctoral thesis consists of three chapters which are focused on the analysis of monetary policy in emerging economies. In particular, Chapter 2 measures the output cost of disinflation namely, the sacrifice ratio (SR) for emerging economies with and without Inflation Targeting (IT). Three alternative approaches are adopted: first, disinflationary episodes are identified for individual countries. Second, aggregate supply curves are estimated. Third, a structural VAR model is employed. The results suggest that for countries where the process of disinflation has been accompanied by the implementation of IT, lower and more stable levels of inflation can be achieved. Furthermore, sacrifice ratios have increased as the level of inflation decreases. In Chapter 3, the main determinants of monetary policy in Mexico and Israel are analysed. To this end, reaction functions for each country in terms of forward-looking rules are estimated. The results generally suggest that when setting monetary policy, central banks in these countries look beyond just inflation and output. Moreover, movements in the exchange rate seem to play an important role especially in the case of Israel where there is not a clear commitment to price stability. Chapter 4 investigates the impact of exchange rate behaviour on domestic investment in the Mexican Manufacturing Industry within the context of IT. Standard investment equations are utilised to analyse the role of the level and volatility of exchange rates on investment. The results support the view that a depreciation of the exchange rate has a positive effect through the export channel. Volatility also matters and its effect is mainly observed in those sectors that rely more on exports. Differences are observed within different competitive markets.

The main aim of this thesis is to study the impact of lack of credibility in a transition to price stability on both, the behaviour of the output and the optimal speed of disinflation. The analysis takes place in an environment where the supply-side of the economy is characterized by monopolistically competitive firms, and where there is rigidity in the setting of prices. The effects of a disinflationary monetary policy are studied when policy makers are committed to price stability in the strict sense of achieving and maintaining a constant price-level. However, an expectation updating rule that incorporate a more flexible way of modelling the evolution of agent's priors then previously done in the literature has been employed. Previous work by Ball (1994) and Ireland (1997) identifies the "disinflationary booms" which accompany a disinflation program. They explain their appearance as due to imperfect credibility. In this thesis it is demonstrated that the "disinflationary booms" may or may not disappear in an environment with imperfect credibility, depending on the speed of learning relative to the speed of disinflation. Regarding the optimal speed of disinflation, this thesis suggests that in both cases of perfect and imperfect credibility big inflations should be stopped rapidly. On the other hand, in the case of imperfect credibility, for small inflations, the speed of disinflation decreases in comparison to the case of perfect foresight. Also, once inflation has risen substantially, imperfect credibility makes sizeable output losses in the transition to price stability highly likely even when the speed of disinflation is 'optimal'.

In Chapter 1 I develop a simple model, that builds upon some previous work on financial innovation processes, to account for the main stylized facts observed during extreme hyperinflations. The modeling device used here helps to reconcile some conflicting views on the causes, development and end of a hyperinflation without departing from the rational expectations assumption. Specifically, it is shown that the effectiveness of a future orthodox reform to preclude the occurrence of a hyperinflation, either speculative or fundamental, is an endogenous outcome which depends on a wide array of policy choices (fiscal and monetary) and structural features of the economy. In Chapter 2 I examine the postulates of the Fiscal Theory of the Price Level (FTPL) under an interest rate peg. I show that the usual definition of a non-Ricardian plan involves a non-credible government policy commitment, thus confuting the interpretation of the FTPL as a policy-based equilibrium selection device. Then I identify the set of necessary conditions for the implementation of non-Ricardian fiscal plans that result in a unique equilibrium. A critical necessary condition for the credibility of a fiscalist plan is that the equilibrium level of seigniorage must be non-positive. I argue that the fiscalist stock-analogy is only meaningful, precisely, when money enters into the government constraint as a destination of funds, rather than as a source. In Chapter 3, I extend Buiter's (2001, 2002) criticism (non-Ricardian plans are generally non-implementable whenever the monetary authority sets a non-contingent sequence of money supplies) to an infinite horizon economy. In particular, it is shown that a fiscalist deflation involves the violation of a household's optimality condition and that the notion of a fiscally-induced speculative hyperinflation cannot be rationalized invoking a symmetry between the problem of pricing a potentially fiat non-convertible asset (like money) and that of pricing the stock of a private firm as advocated by the FTPL.

Inflation targeting has been the central focus of monetary policy since early 1990s as more than 60 central banks across the countries target it explicitly, others target it implicitly. However, how precisely does the central bank target inflation in practice? Does monetary policy always only respond to inflation or does it also react to asset prices and open economy variables? This thesis models these aspects of monetary policy primarily focusing to the UK inflation targeting regime. The empirical results are significant. First, monetary policy in UK is forward looking. It responds to deviations of inflation from the target, to the output gap and to asset prices misalignments. The policy reaction to inflation is strongest followed by the reaction to the output gap, the foreign interest rate, the exchange rate, house prices and share prices. Second, monetary policy is nonlinear because (a) it has deflationary bias, (b) it responds to asset prices only when asset prices misalignments are high, and (c) it responds to the output gap only when it does not respond to inflation and asset price misalignments. Third, policy response to exchange rates does not depend on inflation regime while the reaction to inflation does depend on the exchange rate regime. Fourth, policy response to inflation is asymmetric and it aims to keep inflation within a range rather than pursuing a point target of 2.5%. Fifth, neither the exchange rate misalignment nor the foreign interest rate alone can capture the open economy effects; policy responds to both variables.

Στην παρούσα διπλωματική εργασία παρουσιάζεται μια μαθηματική προσέγγιση της θεωρίας κινδύνου. Η ποσοτικοποίηση των κινδύνων είναι σημαντική τόσο για τους χρηματοοικονομικούς οργανισμούς όσο και για τις ρυθμιστικές αρχές, ώστε να εξασφαλίζεται η επάρκεια των χρηματοοικονομικών ροών και η ασφάλεια των κεφαλαίων. Αρχικά αναφερόμαστε σε δύο σημαντικές μεθόδους μέτρησης κινδύνου, την Αξία-σε-Κίνδυνο (VaR) και το Αναμενώμενο Κατώφλι (Expected Shortfall), καθώς και στην σχέση μεταξύ τους. Στην συνέχεια επικεντρωνόμαστε στον υπολογισμό του κινδύνου αγοράς μέσω των μεθόδων διασποράς-συνδιασποράς, ιστορικής προσομείωσης και Monte Carlo. Ακολουθούν δύο στοιχειώδεις προσεγγίσεις του λειτουργικού κινδύνου: η προσέγγιση με βασικό δείκτη (BI) και η τυποποιημένη προσέγγιση. Ιδιαίτερη μελέτη πραγματοποιήθηκε στα μοντέλα μέτρησης του πιστωτικού κινδύνου που διακρίνονται στα κατασκευαστικά και τα μοντέλα μειωτικού-τύπου. ‘Ενας ακόμα σημαντικός κίνδυνος είναι ο συνιστάμενος, που συμβάλλει στην εύρεση ορίων, καθώς και στη διανομή του κεφαλαίου στους επιμέρους κινδύνους επιτυγχάνοντας την ασφάλεια της επένδυσης. Τέλος, αντικείμενο μελέτης αποτελούν τεχνικές που εφαρμόζουν τις παραπάνω μεθόδους μέτρησης κινδύνων στην οικονομία και πιο συγκεκριμένα στον χώρο των ασφαλίσεων. / -

Στην παρούσα εργασία γίνεται μια ανασκόπηση της μεθόδου μέτρησης κινδύνου Value at Risk (VaR). Παρουσιάζουμε μερικούς βασικούς τρόπους μέτρησης του Value at Risk και εφαρμόζουμε σε δεδομένα ενός χαρτοφυλακίου συναλλαγματικών ισοτιμιών και στον γενικό δείκτη του χρηματιστηρίου Αθηνών διαφορετικά μοντέλα GARCH (IGARCH, TGARCH, EGARCH, GARCH) για την εκτίμηση του VaR με ορίζοντα μιας ημέρας (1- day ahead). Εφαρμόζουμε διαφορετικές υποθέσεις για την κατανομή των αποδόσεων (normal, student's-t, ged), χρησιμοποιούμε διαφορετικά μεγέθη δείγματος (250, 500, 750, 1000) και επίπεδα εμπιστοσύνης για το VaR (95% και 99%). Στην συνέχεια τα αποτελέσματα τού κάθε μοντέλου ελέγχονται με βάση τον έλεγχο του Kupiec για την καταλληλότητα τους. / In the present diplomatic essay we present a review of the method for risk measurement Value at Risk (VaR). We present a few basic ways of measuring Value at Risk and apply to data of an exchange rates portfolio and Athens stock exchange index different GARCH (IGARCH, TGARCH, EGARCH, GARCH) models for the estimation of the 1-day ahead VaR. We use various assumptions for the distribution of the returns (normal, student's-t, ged), various sample sizes (250, 500, 750, 1000) and VaR confidence levels (95% and 99%). Then the results of each model are tested using Kupiec test for their performance.

Η πολύπλοκη μορφή που απέκτησαν οι χρηματοοικονομικές αγορές κατά τη διάρκεια των δύο τελευταίων δεκαετιών, είχε ως αποτέλεσμα την απώλεια πολύ υψηλών κεφαλαίων από τις επιχειρήσεις και από τις τράπεζες. Η ανάγκη για συστηματική μέτρηση του χρηματοοικονομικού κινδύνου οδήγησε στην επινόηση του μεγέθους της αξίας σε κίνδυνο (Value-at-Risk, VaR). Η μέθοδος αυτή παρέχει στον ενδιαφερόμενο έναν αριθμό που εκφράζει τη μέγιστη αναμενόμενη ζημία μίας επένδυσης για δεδομένη χρονική περίοδο και δεδομένο επίπεδο εμπιστοσύνης. Παρά το γεγονός ότι η VaR έχει κάποιους περιορισμούς που απαιτούν τη χρήση stress test και scenario test, συνολικά, η VaR είναι η καλύτερη ανεξάρτητη τεχνική μέτρησης των κινδύνων που είναι διαθέσιμη. Στόχος της παρούσας διπλωματικής εργασίας είναι η μέτρηση της VaR ενός χαρτοφυλακίου. Επιπλέον, μέσα από αυτήν την εργασία θα γίνει κατανοητό τι είναι η VaR, πώς μπορεί να υπολογιστεί, ποια είναι τα κύρια χαρακτηριστικά της και ποια είναι τα πλεονεκτήματα και τα μειονεκτήματά της. Τέλος, ιδιαίτερη έμφαση δίνεται στην παρουσίαση των μεθόδων υπολογισμού της VaR. / The inextricable form of the financial markets during the last two decades result in the loss of high capital from the businesses and banks. The need of a systemic measurement of the financial risk leads to the invention of the Value-at-Risk method. This method provides the interested person with a number which expresses the potential maximum loss of an investment for a given period of time and a given confidence level. Despite the fact that VaR has some restrictions demanding the use of stress test and scenario test, altogether, VaR is the best independent measuring technique of the risks that it is available. The aim of this dissertation is to measure the VaR of a portfolio. Moreover, it will be registered what VaR is, how it can be measured, which are its main characteristics, its advantages and disadvantages. Lastly, more emphasis is given to the presentation of the measuring methods of VaR.