Modifying scoring data based on historical changes

A system comprising:

• one or more computers programmed to perform operations comprising:
• calculating a plurality of quality of result statistics for a first document as a search result for a first query, each of the quality of result statistics corresponding to a different respective time period;
• calculating a plurality of time trend statistics, the time trend statistics estimating changes in the quality of result statistics over time, wherein each of the time trend statistics comprises a quality of result difference between a respective first quality of result statistic and a respective second quality of result statistic of the quality of result statistics;
• generating a first modified quality of result statistic by modifying a first quality of result statistic for the first document as a search result for the first query by a factor, where the factor is based on, at least, a rate of change of the time trend statistics;
• and
• providing the first modified quality of result statistic as an input to a document ranking process for the first document and the first query.

A computer-readable storage medium having instructions stored thereon that, when executed by one or more computers, cause the computers to perform operations comprising:

• calculating a plurality of quality of result statistics for a first document as a search result for a first query, each of the quality of result statistics corresponding to a different respective time period;
• calculating a plurality of time trend statistics, the time trend statistics estimating changes in the quality of result statistics over time, wherein each of the time trend statistics comprises a quality of result difference between a respective first quality of result statistic and a respective second quality of result statistic of the quality of result statistics;
• generating a first modified quality of result statistic by modifying a first quality of result statistic for the first document as a search result for the first query by a factor, where the factor is based on, at least, a rate of change of the time trend statistics;
• and
• providing the first modified quality of result statistic as an input to a document ranking process for the first document and the first query.