20. The system of claim 18 , wherein determining Q comprises determining Q from a maximum Max(QFval) of one or more of the following query freshness values: a percentile value of a number of occurrences of the query being received within a first recent time period; percentile value of a number of occurrences of the query on blog web pages within a second recent time period; a percentile value of a number of occurrences of the query on news web pages within a third recent time period; a percentile value of a number of occurrences of the query on social network web pages within a fourth recent time period; a percentile value of a number of occurrences of the query requesting news search results within a fifth recent time period; a percentile value of a ratio of a number of occurrences of the query requesting news search results within a sixth recent time period to a number of occurrences of the query requesting web search results within the sixth recent time period; a percentile value of a number of user selections of news search results provided in response to the query within a seventh recent time period; and a percentile value of a ratio of a number of user selections of news search results provided in response to the query within an eighth recent time period to a number of user selections of web search results provided in response to the query within the eighth recent time period.
18. The system of claim 17 , wherein the boosting function is a continuous function having a range of values that includes values less than 1, a value equal to 1, and values greater than 1, whereby the product of S and the value of the boosting function can be less than S, equal to S, or greater than S.