This study uses 1,036 firm-year data of non-financial firms listed in the Stock Exchange of
Thailand (SET) during 2003-2007. Most of the data can be obtained from SETSmart
database provided by the SET. SETSmart database provides firm-level data including
financial statements and financial ratios, ownership of shareholders with 0.5 percent or more
shareholding, list of directors, and company files (form 56-1) which all public companies are required to submit to the SET annually. Form 56-1 contains extensive details of family
relationship among top management and their shareholding, and details of aggregate
shareholding of the controlling family and ultimate shareholders of private firms. Missing
details of family relationship is supplemented by the work of Polsiri and Wiwattnanakantang
(2006). Other supplementing sources of data include the company web sites, SET’s official
web site, and Business on Line database (BOL).