This thesis is a collection of three essays on firm dynamics and development. These essays consider the interaction between the dynamics of allocative efficiency and economic growth from the three different perspectives. The first essay quantitatively analyses the role of allocative efficiency in explaining growth miracles. It builds a heterogeneous firm model with entry and exit. The model economy converges to a more efficient steady state by selecting more productive firms and reallocating resources to them. Frictions obstruct firm selection and labour reallocation and delay the convergence for decades. Meanwhile, slow efficiency improvement continuously increases productivity a...