I want to know the answer to the following question:
What year did a change in DST policy cost North America somewhere between $500 million and $1 billion in extra work?
All the background I'm provided with is that "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.". Is that enough to answer the question?