Twenty years after the introduction of the theory, we revisit what it does—and doesn’t—explain. by Clayton M. Christensen, Michael E. Raynor and Rory McDonald Please enjoy this HBR Classic. Clayton M.

Global healthcare spending is $9.8 trillion annually, with the U.S. accounting for about $4.9 trillion. Investors can consider drug, medical device, payer, and healthcare provider stocks. Focus on ...