Alternative Emhs The strong-form EMH contends that stock prices reflect all information from public and private sources relevant to the firm, including information available only to company insider. It extends the assumption of efficient markets to assume perfect markets in which all information is cost -free and available to everyone at the same timeAlternative EMHs • The strong-form EMH contends that stock prices reflect all information from public and private sources relevant to the firm, including information available only to company insider. – It extends the assumption of efficient markets to assume perfect markets in which all information is cost-free and available to everyone at the same time