Sharing research results with the world is key to the progress of your discipline and career...
Open access removes geographic and socioeconomic barriers to knowledge, and enables all researchers to read, cite, and build upon your work. By making your work open access, you are furthering the democratization of knowledge and contributing to a greater understanding of our world.
Because open access work is more widely available, readers are more likely to find and cite your work (as found in a number of studies).
Open access is about more than just access, it's about reuse. When you retain some or all of your author rights, you can upload your work to your own website or institutional repository, distribute your work to colleagues, and use your work in your own teaching.