Part of my response to this question on QUORA:
“Not long ago, I wrote a book on investment strategies. As you can imagine, there were a lot of figures to seek out, especially when establishing the historical track record of the stock market and finding sample stocks to illustrate various points. This research followed three steps:
1. The client sent me whatever he had collected.
2. I searched the Internet for data to fill in the holes, even though “no research” was in place for this contract.
3. I asked the client to complete the hole-filling that I could not easily do.”