Proceedings

statements. The study examines the contents of the entire annual report, which was
filed in the last year of the VFP, not just the financial statement part, as has typically
been empirically investigated in previous work on voluntary disclosure. Thus, the
sample of 51 firms includes all voluntarily filed annual reports of 2008. Following
Gray et al. (1995), the entire annual report is seen as a disclosure package. The focus
on the annual report is not the only way by which companies voluntarily provide
information to investors or other interested parties. For example, conference calls and
analyst meetings can provide relevant information to stock market participants
(Debreceny et al. 2002; Healy and Palepu 2001; Frankel et al. 1999). Nevertheless,
the annual report is the most widely disseminated source of information on publicly
and privately held firms (Arnold et al. 1984; Chang et al. 1983; Gray et al. 1995). The
extent of voluntary disclosure is measured by a disclosure index with 54 items.
Moreover, I examine voluntary disclosures by type of information, namely financial,
non-financial, and general information. This procedure is supported by the
expectation that there may be differences in the disclosure behavior of firms
depending on the type of information (Gray et al. 1995). As in recent studies, this
paper considers the hypothesis that certain firm-specific variables may explain the
observed variation in voluntary disclosure. Following Lang and Lundholm (1993),
independent variables were categorized in structure-related variables, performancerelated
variables, and market-related variables.
The study provides several interesting findings. The findings show that voluntary
filers predominantly provide financial tagged information to financial statements
users. However, contrary to earlier research (e.g., Boritz and No 2008), the results
indicate that due to more experience in XBRL filings, firms included notes and
Management Discussion & Analysis (MD&A) in their filings. Thus, the development
of XBRL taxonomies for narrative parts of the annual report is becoming increasingly
important. The results show that firm size and the level of innovativeness of the firm,
measured by the ratio R&D expenditures to sales, to be significantly and positively
related to the extent of voluntary disclosure. Both variables also seem important in
explaining the sub-category financial information disclosures.
The potential contributions of this current study are several. First, examining the
voluntary disclosures of U.S. listed companies should be useful worldwide for
companies that are thinking about adopting XBRL. These companies have a likely
interest in knowing how other firms have followed the complex cost-benefit trade-offs
associated with voluntary disclosures in XBRL format. In addition, voluntary
disclosures often foreshadow trends in worldwide financial reporting and research on
voluntary disclosure will represent an addition to knowledge. Second, the acceptance
and implementation of XBRL around the world has considerably grown during the
last few years. For example, in Europe, a wide range of European countries have
admitted the voluntary submission of financial statements in XBRL format. Still,
several other countries in Europe, such as Lithuania, Czech Republic, and Slovenia, as
well as large parts of Africa and Asia, have not yet dealt with the implementation of
XBRL business reporting at all. Consequently, the results of this study might be
relevant for governments that consider regulating XBRL business reporting for listed
and not listed firms and developing XBRL taxonomies at the national level. However,
only national taxonomies are not able to correspond to the increasing demand for
standardization and comparability on capital markets (Wagenhofer 2003). Therefore,
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