[Rsquared]

All of above is technically correct.

However, the answer is quite simple... it is a function of supply and demand. As demand increases (or supply declines), price goes up. As demand declines (or supply increases), price goes down. In the fixed income market, yield is inversely related to price. Price goes up, yield goes down. Price goes down, yield goes up. See JYL's example above.

So if demand increases, price goes up and yield goes down.

By the way, it's called the fixed income market because of the "fixed coupons" earned on bonds.