Read this and answer the question. If the question is unanswerable, say "unanswerable".

The second half of the 20th century to the present has seen a gradual shift towards improved human rights for Aboriginal people. In a 1967 referendum over 90% of the Australian population voted to end constitutional discrimination and to include Aborigines in the national census. During this period many Aboriginal activists began to embrace the term "black" and use their ancestry as a source of pride. Activist Bob Maza said:

What year was constitutional discrimination ended?
1967