2019年第一季，證交所宣布強制所有上市櫃公司採用iXBRL (inline XBRL)格式取代XBRL (eXtensible Business Reporting Language)格式編製財務報表。採用iXBRL格式編製財務報表相較於採用XBRL格式編製，可以提升財務報表的可讀性、正確性、分類標準的靈活度以及降低軟體開發成本，進而提升財務資訊揭露品質，增加公司的資訊揭露水準。 本研究以買賣價差做為衡量資訊不對稱的代理變數，以台灣2018年6月至11月及2019年6月至11月分別取各6個月，共12個月之每日股價資料計算買賣價差，衡量採用iXBRL前後資訊不對稱程度的變化，並探討公司規模大小及機構投資人持股比例高低受影響的程度。實證結果顯示：( 1 )採用iXBRL格式編製財務報表能降低資訊不對稱；( 2 )在其他條件不變下，小型公司採用iXBRL格式編製財務報表相較於大型公司更能降低資訊不對稱；( 3 )在其他條件不變下，機構投資人持股比例較低的公司採用iXBRL格式編製財務報表相較於機構投資人持股比例較高的公司更能降低資訊不對稱。 ;In 2019 Q1, Taiwan Stock Exchange Corporation (TWSE) proposed a regulation that all listed companies in Stock Exchange Market and Over-the-Counter Market must disclose their financial statements in inline XBRL (iXBRL) format instead of eXtensible Business Reporting Language (XBRL) format. Disclosure of financial statement in iXBRL format, compared to XBRL format can enhance readability, accuracy, flexibility of Taxonomy and reduce costs of software development in processing iXBRL instance documents. In this paper, I use bid-ask spread as proxy of information asymmetry. I use daily stock price data to calculate bid-ask spread in the period from June to November in 2018 and the same period in 2019 in order to measure the change of information asymmetry before and after the regulation of using iXBRL format to disclose financial statements. I also compare the difference of impact between size of companies and institutional ownership. The empirical result shows: First, disclosing financial statements in iXBRL format can reduce information asymmetry. Second, compared to larger companies, ceteris paribus, smaller companies tend to benefit more from the adaption of disclosing financial statements in iXBRL format. Third, compared to firms with higher institutional ownership, ceteris paribus, firms with lower institutional ownership tend to benefit more from the adaption of disclosing financial statements in iXBRL format.
