Extended XBRL Taxonomies and Financial Analysts' Information

I investigate how the use of extended tags in eXtensible Business Reporting Language (XBRL) filings is associated with financial analysts' forecast error and dispersion. The SEC allows firms to provide customize tags in their XBRL filings which, on the one hand, may allow firms to customize financial statements to reflect firms specific disclosures. On the other hand, customized tag may inhibit information search and ultimately reduce the usefulness of XBRL data. Since the use of extended tags is related to the reporting environment of the firm, I employ an instrumental variables technique to control for endogeneity. I find extensions are robustly negatively related to analysts' forecast error and dispersion after controlling for endogeneity. In additional analysis, I find that extensions in the footnote disclosures drive this negative relationship and that extensions in the financial statements are marginally positively associated forecast error and dispersion, controlling for extensions is the footnote disclosures. This study is relevant to regulators creating policies about XBRL extensions