This is because China's export volume is relatively large, resulting in a large amount of foreign exchange reserves, of which the US dollar is the main reserve. It is not that China wants to buy US Treasury bonds, but that China implements appropriate foreign exchange controls. The dollars obtained by enterprises' export must be converted into RMB, that is, more RMB will be issued if there are more reserves. As for whether it is controlled by people, it is hard to say. The landlord's question is too vague, so it's easier to answer it specifically.