And it's during this time period that the Song Dynasty is able to leverage a more robust rice seed from Southeast Asia that allows it to feed many, many more people. And so this obviously allows a population growth, but any time you're able to feed people and there's more prosperity, you're going to have a more stable empire. Now another major input into prosperity and the stability of empires is the notion of trade. And China had always many river systems which helped facilitate agriculture and trade. But as you get into the Sui Dynasty, right over here, you have the completion of the Grand Canal, which is even today the largest man-made canal. It stretches from Beijing to Hangzhou and actually goes beyond that and has other tributaries. And that, connected with the existing river systems, allowed for a lot of trade to happen, especially as we get into the Tang and the Song Dynasties.