This paper traces the evolution of the time series tradition in the study of market structure, focusing on the work of Robert Gibrat and its impact on recent research. Gibrat's *Inégalités Économiques* introduced the Law of Proportional Effect, suggesting that the growth rate of a firm is proportional to its current size. This model was later applied to income distributions and plant sizes in manufacturing, showing striking fits. However, the literature evolved to address issues such as sample censoring, heteroscedasticity, and the role of firm age and size in growth. Recent studies have shifted towards stochastic elements in maximizing models, exploring the life cycle of industries and the evolution of market structure over time. The paper also discusses the concept of turbulence, where entry and exit rates are positively correlated across industries, and the implications for firm size distributions. The findings suggest that the size distribution of firms may be influenced by independence effects and strategic interactions within submarkets, leading to a bound on skewness that is relatively sharp.This paper traces the evolution of the time series tradition in the study of market structure, focusing on the work of Robert Gibrat and its impact on recent research. Gibrat's *Inégalités Économiques* introduced the Law of Proportional Effect, suggesting that the growth rate of a firm is proportional to its current size. This model was later applied to income distributions and plant sizes in manufacturing, showing striking fits. However, the literature evolved to address issues such as sample censoring, heteroscedasticity, and the role of firm age and size in growth. Recent studies have shifted towards stochastic elements in maximizing models, exploring the life cycle of industries and the evolution of market structure over time. The paper also discusses the concept of turbulence, where entry and exit rates are positively correlated across industries, and the implications for firm size distributions. The findings suggest that the size distribution of firms may be influenced by independence effects and strategic interactions within submarkets, leading to a bound on skewness that is relatively sharp.