题目里问到在low interest rate环境下，买fixed annuiry有什么缺陷
答案里有一句
When buying a fixed annuity the investor locks in payments based on current interest rates. Purchase of a large fixed annuity when interest rates are low will lock in relatively low payments
这句怎么理解啊？
我一直理解的是fixed income 的purchase price等于未来所有payment折现求和，所以当low interest rate情况下，会造成相同payment的purchase price高，不知道这么答对吗？