It's Earth Day, so naturally we can all expect a peppering of messages from companies telling us that we can all take steps to save the planet, starting with our own carbon footprints. Ever wondered where the idea of the personal carbon footprint came from, and why companies don't talk about their own footprint...? On Earth Day (and every day) sustainable investing remains one of the most powerful tools we have available to change the way companies treat the natural world. We think the corporate footprint is where we need to be focused. What are your thoughts?