This task is about creating an unanswerable question based on a given passage. Construct a question that looks relevant to the given context but is unanswerable. Following are a few suggestions about how to create unanswerable questions:
(i) create questions which require satisfying a constraint that is not mentioned in the passage
(ii) create questions which require information beyond what is provided in the passage in order to answer
(iii) replace an existing entity, number, date mentioned in the passage with other entity, number, date and use it in the question
(iv) create a question which is answerable from the passage and then replace one or two words by their antonyms or insert/remove negation words to make it unanswerable.

Passage: The island's unique social and economic organisation has evolved over the years, but is based on the principles set out by William Glass in 1817 when he established a settlement based on equality. All Tristan families are farmers, owning their own stock and/or fishing. All land is communally owned. All households have plots of land at The Patches on which they grow potatoes. Livestock numbers are strictly controlled to conserve pasture and to prevent better-off families from accumulating wealth. Unless it votes for a change in its law, no outsiders are allowed to buy land or settle on Tristan; theoretically the whole island would have to be put up for sale. All people including children and pensioners are involved in farming, while adults additionally have salaried jobs working either for the Government, or, a small number in domestic service, and many of the men are involved in the fishing industry, going to sea in good weather. The nominal fishing season lasts 90 days; however during the 2013 fishing season 1 July through 30 September there were only 10 days suitable for fishing.
What is based on principles put into place by William Glass in 2013?