According to recent domestic and international studies, claims have been raised that the balance sheet, which represents a firm's financial condition, fails to accurately reflect the firm's true value due to the omission of intangible assets, and that the efficiency of traditional financial statements has been declining. At the same time, when expenditures of an intangible nature are treated as expenses, it becomes correspondingly more difficult for firms to realize net income. This study focuses on the increase in intangible asset-related expenditures and the increase in loss-reporting firms accompanying the transition from an industrial society to a knowledge-based society, and examines the trend of changes in the usefulness of accounting information over the past two decades. As investment in intangible assets has recently increased, the information asymmetry of firms with a high proportion of intangible assets has become severe, and as a result, increases in firms' cost of capital and transaction costs for investors and stakeholders appear to have been induced. Ultimately, if firms are not fairly valued in the stock market due to the absence of recognition and measurement of intangible assets, their intrinsic value will be undervalued, which will lead to the avoidance of R&D investment in knowledge industries. According to the research results, the ratio of R&D expenditures to sales and the number of loss-reporting firms have been continuously increasing since the 1990s, and consequently, the usefulness of accounting information as measured by the explanatory power of the Ohlson model has been relatively decreasing. This decrease in the usefulness of accounting information was observed to be attributable to the increase in R&D expenditure ratios and loss-reporting firms. In addition, in the analysis of the value relevance of intangible asset-related expenditures around the 1998 revision of accounting standards, the stock market's valuation of capitalized development costs and expensed R&D expenditures showed significant differences before and after the 1998 revision of accounting standards.