 The reality is the production of commodity chemicals, the production method, tends to change every 50 or 100 years. It takes a long time. The global economy really has to change in order to make a new system more economical. For over a century, limestone was the most economical way to make cement, but there's been some massive structural changes in the economy that have made a pretty recent phenomena that we no longer think limestone is the most economical way to make cement.