reason that we are so productive a has to do with the diverse set of industries that we have our entreprenure, which the best in the world. the flexibility of our labor markets and our capital markets. and our technology, which remains one of our very strongest points. increasingly technology has been driving economic growth. and with some of the finest yooifts in the world and researchers centers and as a magnet for talented people from around the world, the united states has been very successful in the research and development area. so that has also been a source of ongoing growth and innovation in our economy. now, again, we have weaknesses and the financial crisis highlighted a few. but we've always tried of course to address that. i'll come back to it biening our financial regulatory system. here's a picture i find kind of interesting. to put a little perspective on what we've been talking about for the last few lectures. the dashed line shows a constant growth rate of a little over 3% in real terms. this is a means a constant growth rate. you can see that the united states economy going