This thesis investigates two economic policy dimensions in contemporary world economy. The first chapter focuses on the recent accumulation of international reserves by central banks in developing economies. I present a simple model of reserve management where a central bank accumulates reserves in order to avoid spikes in inflation during financial crises. This monetary perspective helps to account for the massive accumulation of reserves observed in the data. The second chapter turns to financial reform, with an emphasis on the role played by savings. I show how imperfect competition in the financial sector can internalize externalities and yield larger investment when domestic savings are low. Taking this view allows for a better understanding of the empirical relationship between financial reforms and economic growth. / Aquesta tesi investiga dues dimensions de la poltica econ´omica en l’economia mundial contempor`ania. El primer cap´ıtol es centra en la recent acumulaci´o de reserves internacionals per part dels bancs centrals en les economies en desenvolupament. Exposo un model senzill de gesti´o de reserves per part d’un banc central que acumula reserves amb l’objectiu d’evitar els augments pronunciats d’inflaci´o durant les crisis financeres. Aquesta perspectiva monet`aria ajuda a explicar l’acumulaci´o massiva de reserves que s’observa en les dades. El segon cap´ıtol es focalitza en la reforma financera, emfasitzant el paper de l’estalvi. Demostro com la compet`encia imperfecta en el sector financer pot internalitzar les externalitats i aix´ı generar m´es inversi ´o, concretament quan l’estalvi ´es baix. L’adopci´o d’aquest punt de vista permet entendre millor la relaci´o emp´ırica entre les reformes financeres i el creixement econ`omic.