Context: Changing clocks and DST rules has a direct economic cost, entailing extra work to support remote meetings, computer applications and the like. For example, a 2007 North American rule change cost an estimated $500 million to $1 billion, and Utah State University economist William F. Shughart II has estimated the lost opportunity cost at around $1.7 billion USD. Although it has been argued that clock shifts correlate with decreased economic efficiency, and that in 2000 the daylight-saving effect implied an estimated one-day loss of $31 billion on US stock exchanges, the estimated numbers depend on the methodology. The results have been disputed, and the original authors have refuted the points raised by disputers.

Question: What year did a change in DST policy cost North America somewhere between $500 million and $1 billion in extra work?
Answer: 2007

Question: Who is the economist who said there was about $1.7 billion in lost opportunity costs because of the 2007 changes?
Answer: William F. Shughart II

Question: What have some people argued correlates with time shifts from daylight savings?
Answer: decreased economic efficiency

Question: What do some call the effect that they say caused a one-day loss for stock exchanges of approximately $31 billion in the year 2000?
Answer: the daylight-saving effect

Question: What factor determines the numbers people reach for estimates when studying DST?
Answer: methodology