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• Statistical Inference 统计推断
• Statistical Computing 统计计算
• (Generalized) Linear Models 广义线性模型
• Statistical Machine Learning 统计机器学习
• Longitudinal Data Analysis 纵向数据分析
• Foundations of Data Science 数据科学基础

## 经济代写|产业经济学代写Industrial Economics代考|Data sample

Table $5.1$ summarizes basic features of the data sample used in this study. The sample includes 30 chemical products, each of which experienced chronic decline in US domestic output and capacity. Data were collected from the peak year of output or capacity (whichever occurred earlier) through the start of $1987 .{ }^{3}$ On average, output declined by 42 per cent and capacity by 38 per cent from the historical peak. The magnitudes of capacity and output reduction were strongly (but far from perfectly) correlated, with $r=0.64$. The number of producers fell by an average of 32 per cent, nearly the same as industry capacity.

The data were obtained from chemical producer listings compiled by SRI International, supplemented by government and industry sources. The capacity data are from annual issues of the Directory of Chemical Producers, published by SRI International. This directory reports US production capacities by product, firm, and plant, observed at the start of each calendar year. Output data were collected from various sources. ${ }^{4}$ Chemical trade journals were consulted to determine why products in the sample were in decline.

The sample products were selected as follows. The Directory of Chemical Producers includes annual capacity listings for approximately 240 products. Output data were collected on each of these products to identify those that were declining. The sample includes all products with published capacity data that were observed to be declining over a period of five years or more through to the end of $1986 .{ }^{5}$ The sample is believed to be a fairly representative cross-section of commodity product industries in decline. ${ }^{6}$
The last column of table $5.1$ summarizes the reasons why demand was falling for products in the sample. Decline often stemmed from a combination of factors. Three products had been found to be environmentally hazardous and were being restricted or phased out by regulatory agencies. Seven products served as inputs in the manufacture of downstream products that had been found hazardous. An additional seven products were being replaced by direct substitutes, and three products faced such replacement downstream. For three products, changes in downstream manufacturing processes reduced or eliminated demand for the product as an input. For seven products, competition from lower-priced imports was a factor contributing to the decline in US output.

## 经济代写|产业经济学代写Industrial Economics代考|Empirical results at the firm level

Tables 5.2-5.7 give summary statistics on various characteristics of the capacity reduction process, measured at the firm level.

Table $5.2$ describes changes in producer concentration over the sample period. For each product, the table gives the change in the Herfindahl concentration index $(H)$, the number of producers $(N)$, and the coefficient of variation in firm sizes $(V){ }^{9}$ The products in table $5.2$ have been sorted in decreasing order of the percentage decline in total industry capacity. Given that a small amount of entry occurred over the coverage period, ${ }^{10}$ two separate counts of the number of producers are provided for the terminal year: the total number of firms observed and the number of survivors remaining from the peak year. Similarly, two figures are reported for changes in the coefficient of variation: the first compares the size distribution of all producers in the peak year with the size distribution of all producers in the terminal year, whereas the second is computed over the subset of firms that survived from the peak year through the terminal year.

Table $5.2$ reveals several strong tendencies. First, producer concentration increased for most products in the sample. Twenty-six products exhibited increases in the Herfindahl index, while four products exhibited slight decreases.

Given the identity relation, $H=\left(V^{2}+1\right) / N$, the observed increase in the Herfindahl index implies a reduction in the number of producers or an increase in the coefficient of variation of firm sizes (or both). Table $5.2$ gives clear evidence of the former: all but three products had a reduction in the number of producers over the coverage period. There is, however, no evidence of increased variation in firm sizes. Indeed, table $5.2$ documents a general pattern of firm size convergence; the coefficient of variation declined for more than three-fourths of the products in the sample. This size convergence could reflect one or more underlying processes: (1) disproportionate exit of large firms, (2) disproportionate exit of small firms, (3) disproportionate shrinkage of large firms, or (4) disproportionate growth of small firms.

# 产业经济学代考

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