Couldn't the company data be manipulated by them and therefore of less value?

Pharmaceutical companies, as with all publically listed companies, are required by law to disclose financial information and have no incentive to provide inaccurate information to the marketplace. In addition, RiskMetrics, the company that is responsible for the research and development of the Index, conducts spot checks on the provided industry data to ensure it is both up-to-date and valid.