补充一下，2 x 和 3x 长期损耗和表现不好的主要原因如下：

They need to maintain a daily leverage of 2x or 3x . So, they got an automatic re-balancing problem… for example,the long 2x and 3x are buying assets when prices are increasing and selling assets when the prices are decreasing in order to maintain the leverage ratio. 

For example:

If a 2x has its own money of $100, it need to borrow $100 and buy $200 of security, (Total =$200)

when the price of the security drops 10%, total = $180, it own money drops to $80, the borrowed stays at $100

In order to maintain the leverage ratio, 2x needs to sell $20 of the security (the $20 returns to the borrower). As the result, it has $80 of its own and $80 borrowed. （Total = $160)

when the price of the security increases 10%, total = $220, it own money increases to $120, the borrowed stays at $100

in order to maintain the leverage ratio, 2x needs to buy $20 of the security. As the result, it has $120 of its own and $120 borrowed. (Total = $240)

Constantly sell low and buy high especially when price goes up and down frequently can cause underperformance.