Table 1. Comparison of the user click-through rate of best match versus the previous TF–IDF method and the default date sort order.

Ranking Method	CTR@20	CTR@10	CTR@5	CTR@3
Sort by date	0.32	0.29	0.24	0.20
Sort by TF–IDF	0.36	0.33	0.29	0.25
Sort by Best Match	0.39	0.36	0.32	0.28

All improvements in CTRs by Best Match are statistically significant with 99% confidence (paired t test). Abbreviations: CTR, click-through rate; TF–IDF, term frequency–inverse document frequency.