Detailed Instructions: This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.
Q: These scholars suggest, from their studies of economic and social data, that early 20th-century child labour in Europe and the United States ended in large part as a result of the economic development of the formal regulated economy, technology development and general prosperity. Child labour laws and ILO conventions came later. Edmonds suggests, even in contemporary times, the incidence of child labour in Vietnam has rapidly reduced following economic reforms and GDP growth. These scholars suggest economic engagement, emphasis on opening quality schools rather than more laws and expanding economically relevant skill development opportunities in the third world. International legal actions, such as trade sanctions increase child labour.
A:
What caused child labour to decrease in the 20th century?