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:
Institute_of_technology

Context:
Since the 1990s, there has been consolidation in New Zealand's state-owned tertiary education system. In the polytechnic sector: Wellington Polytechnic amalgamated with Massey University. The Central Institute of Technology explored a merger with the Waikato Institute of Technology, which was abandoned, but later, after financial concerns, controversially amalgamated with Hutt Valley Polytechnic, which in turn became Wellington Institute of Technology. Some smaller polytechnics in the North Island, such as Waiarapa Polytechnic, amalgamated with UCOL. (The only other amalgamations have been in the colleges of education.)

Question:
In what decade did New Zealand's tertiary education institutions begin consolidation?

1990s