谢谢曹老师出题！下面是我个人的理解，不妥或错误之处，请曹老师和各位老师指正！

句中的 run 是不及物动词，句中的 half a percentage point 是状语（表程度，修饰其后的介词短 below…），below 引导的介词短语也是状语。其实，如果撇开 half a percentage point 这个程度状语不看，句子就变得简单了：

In Britain and Japanin flation is running (half a percentage point) below the rate predicted at the end of last year.

→In Britain and Japan inflation is running below the rate predicted at the end of last year.

类似的句子如：

He is (two years) older than I am.→He is older than I am.

He is (a head) taller than I am.→He is taller than I am.

类似的句子再如：

The submarine is (800 metres) below us. 潜艇在我们下方800米。

They were working (500 metres) below ground. 他们在地下500 米深处作业。

句子大意：英国和日本的通胀比去年年底预测的低了半个百分点。