Both traditional approaches also come with considerable uncertainty about the probability and size of the return on investment .

传统投资方法的另一个问题是无法确定投资是否有回报，而且也无法确定回报的大小。

What can be learnt from these various approaches ?

上面说到的各种方法能带来什么启示？

The two approaches will probably co-exist .

这两种方法将可能并存。

But their approaches differ dramatically .

但是他们采取的方法却大不一样。

There are problems with both approaches .

这两种方法都有问题。