Within the last quarter century, the market value of the S&P 500 companies has deviated greatly from their book value. This "value gap" indicates that physical and financial accountable assets reflected on a company's balance sheet comprises less than 20% of the true value of the average firm. Our further research shows that a significant portion of this intangible value is represented by patented technology.

View the 2009 average intangible asset value for S&P 500 companies within each industry sector (PDFs):

Press Release: OCEAN TOMO ANNOUNCES RESULTS OF ANNUAL STUDY OF INTANGIBLE ASSET MARKET VALUE

INTANGIBLE BOOK VALUE METHODOLOGY
Intangible book value is calculated by subtracting the tangible book value from the market capitalization of a given company or index. In practice, companies report tangible book value per share, number of shares outstanding, and market capitalization. Therefore, intangible book value can be calculated by subtracting the market capitalization from the tangible book value per share multiplied by the number of shares outstanding.

It is expedient to do the calculation on a per share basis, as we have done here, and simply subtract the tangible book value per share from the market price. There are modest discrepancies between the two numbers due to differences in setting shares outstanding on a company by company basis. However, the discrepancy is rarely a few percentage points which are within the error needed for most purposes.