In fact, because inflation has declined, investors in Britain and America have been overcompensated for the risks—a windfall gain that has been exploited by followers of the carrytrade.

实际上由于通胀的下滑，这些货币的投资者所得到的补偿已经超过了所承受的风险。 成为后来跟进的套息交易者的一笔意外横财。

youdao

They have said they would spend the windfall gain from selling 4G licences even though Gordon Brown used the sale of 3G licences to pay down the debt, and even though Labour has said that any windfall from selling bank shares should be used in the same way.

BBC: Labour - what did they mean by that?