Book excerpt: In chapter 2, I study what do changes in top sales shares signal about changes in large firm dynamics. I use an accounting decomposition to identify two sources of top sales shares growth: (i) incumbent top firms grow bigger; (ii) new top firms replace old top firms. I then build a continuous-time random growth model to infer the growth dynamics of firms at the upper tail of firm size distribution. In Chapter 3, in collaboration with Tam Mai, Istudy the implications of occupational and regional inequality on the labor market after the breakout of the COVID-19 pandemic.