You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Political_corruption

Context:
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.

Question:
When did indices on corruption first appear?

1995