17. The system of claim 12 , further comprising instructions to: receive one or more further characters entered into the search field upon display of the refined second list, wherein the second partial query and the further characters represent a third partial query; obtain a third list of query completions for the third partial query; identify one or more query completions in the third list that appear in the refined second list; calculate demotion scores for the identified query completions in the third list, wherein a demotion score for a given identified query completion in the third list is based at least in part on a second period of time between when the refined second list was displayed and when the further characters were entered; use the demotion scores for the identified completions in the third list to demote one or more of the identified query completions to a lesser position in the third list, thereby forming a refined third list; and provide the refined third list of query completions for display on the computing device.
17. The system of claim 12 , further comprising instructions to: receive one or more further characters entered into the search field upon display of the refined second list, wherein the second partial query and the further characters represent a third partial query; obtain a third list of query completions for the third partial query; identify one or more query completions in the third list that appear in the refined second list; calculate demotion scores for the identified query completions in the third list, wherein a demotion score for a given identified query completion in the third list is based at least in part on a second period of time between when the refined second list was displayed and when the further characters were entered; use the demotion scores for the identified completions in the third list to demote one or more of the identified query completions to a lesser position in the third list, thereby forming a refined third list; and provide the refined third list of query completions for display on the computing device. 18. The system of claim 17 , wherein the given identified query completion in the third list further appears in the first list, and the demotion score for the given identified query completion is further based on the period of time between when the first list was displayed and when the additional characters were entered.