The population actually grows from roughly 50 million people during the Tang Dynasty to, it is estimated 100 million people by the Northern Song Dynasty, and eventually keeps growing so that by the time we get to the Ming Dynasty, we have a population of about 200 million people. So what are the things that allows for that population explosion, really? Well, one thing you can imagine is food is very important. 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.