The first paper presents a general equilibrium framework to quantify the welfare impact of firm level shocks in the home country and abroad. We take our framework to data using sectoral level and firm level data from Portugal in 2004. We find that welfare change at home and abroad depends on firms domestic and foreign market shares and also the sector of the firm. Our estimations show that exit of a large firm or a productivity increase of 10% could have significant welfare impacts on consumers up to 1%. Our results also highlight the importance of international trade in transmitting firm level shocks internationally and impacting the welfare of consumers. The second paper presents a general equilibrium framework of trade and multinational production to quantify the impact of changes in corporate tax rates on the location choice of multinational firms and aggregate outcomes. Our model and results show that the British and Swedish tax rate cuts of 2012 increased the welfare of their consumers around half a percentage point at the expense of most of other countries. Financial Crises have always been very costly for the countries who experience them. In the third paper, we focus on the welfare value of the firms that enter or exit during the Portuguese Crisis of 2010-14. We find that the total and average value of exiting firms is much higher than the entering firms during the downturn years, but these values are much closer or even equal during the recovery years. We also realize that the total and average value of exiting firms is much higher during the crisis years compared to recovery years, even though these numbers are almost constant for entering firms.