Mortgage interest rates tied historic lows this week at about 4 3/4 percent. This rate was for the fixed rate, 30 year, conventional (20% down-payment). Wow. This is down from about 6% a year ago, and 6 1/4 % two years ago. Why are the rates so low? The government is still snapping up the majority of mortgage paper, and is slated to do so through early next year.