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From |
"Yi, Bingsheng" <byi@coba.usf.edu> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
st: how to generate groups based on some characteristics and obtain the mean/median value for each group |

Date |
Tue, 18 Jun 2002 19:11:01 -0400 |

Dear Statalisters, I wonder whether you will help me figure out the codes to solve the following problem: I have 12 years panel data containing these four variables: Tobin's q, size, 4-digit industry code (ind4), and id. For each year, I want to make some adjusments in one variable (Tobin's q) based on the other two variables (industry and size). First I need to ensure that there are lat least 10 firms within each industry. If the number of firms within a 4-digit industry code is less than 10, I use 3-digit industry code generated by gen str4 ind3=substr(ind4,1,3), see whether the number of firms with the same 3-digit industry code is greater or equal to 10, if not, then generate and use 2-digit industry code. So in the end there are at least 10 firms within an industry ( which are classified by 4-digit, 3-digit, 2-digit, or 1-digit industry code). The problem is how to get and record the number of firms in each industry. Then within each industry, I want classify firms into three groups based on size, the smallest group contains the smallest 30% firms in size within that industry, the middle group contains the middle 40% firms in size (30% to 70%), and the large group contain firms whose size belongs to the largest 30% in that industry. Then I get the median or mean value of Tobin's q for each of these groups within an industry. the industry-size adjusted Tobin's q = Tobin's q of a firm in an industry - the mean tobin's q of a group to which the firm belongs within the same industry For example, if IBM belongs to the largest size group in computer industry, then the industry-size adjusted Tobin's q of IBM is equal to Tobin's q of IBM - the mean/median value of the largest size group within the computer industry. But I don't know how to generate these groups and obtain the industry-size adjusted Tobin's q for a sample firm. I will greatly appreciate your help!!! Sincerely, Bing * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**st: RE: how to generate groups based on some characteristics and obtain the mean/median value for each group***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

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