This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

Measuring corruption statistically is difficult if not impossible due to the illicit nature of the transaction and imprecise definitions of corruption. While "corruption" indices first appeared in 1995 with the Corruption Perceptions Index CPI, all of these metrics address different proxies for corruption, such as public perceptions of the extent of the problem.
Why is it difficult to measure corruption?