Rapaport Diamond Report
The Rapaport Report is the jewelry industry standard for the pricing of diamonds. The report is published weekly and given to jewelers and diamond merchants to set prices for consumers. The report is issued in the form of a table and prices diamonds based on the 4C's of diamonds - carat, color, clarity and cut . The Rapaport List is copyrighted and available only to subscribers to its magazine.
The Rapaport Group was founded in 1976 by Martin Rapaport. He started the "Rap List" in 1978, used as a baseline for pricing diamonds. The price list only looked at white diamonds because there are more standards for grading, the four C's color, cut, clarity and carat weight. 
While the Rapaport became widely used both within the US and abroad, it was not always considered accurate. IDEX Online came out with their own price list in the early 2000s.