My account usually only holds short positions. I seldom long any stock or ETF. It often keeps 100% cash and 30% margin. Then I think why I don't use the cash to build a low beta portfolio to make some extra money. The requirements for it are 1. 2-4% annul growth, but can't lose more than 2% in any year 2. low correlation with stock market 3. should be in my broker account, and easily cashed to get margin when necessary. Now the only thing in my mind is directly holding US treasury bonds. If 10 year yield rises to 3%, I can just buy and hold it to maturity, although it needs 5-10 years to guarantee return and maybe lose face value sometimes during that. If anyone has any idea about that? thanks.