You cannot use this as an example of a natural experiment. Natural experiment features external variation. In contrast, the amount of liberalization of the econ

You cannot use this as an example of a natural experiment. Natural experiment features external variation. In contrast, the amount of liberalization of the economy likely had a lot to do with the country's history, e.g. Ukraine's markets had been less developed than Estonia's before Soviet Union and as a result they couldn't afford to liberalize as much.