Add documentation for survey item C14a

docs/api/covidcast-signals/fb-survey.md

@@ -287,7 +287,8 @@ data in the estimation procedures described above.
 
 | Signal | Description | Survey Item | Introduced |
 | --- | --- | --- | --- |
-| `smoothed_wearing_mask` | Estimated percentage of people who wore a mask for most or all of the time while in public in the past 5 days; those not in public in the past 5 days are not counted. <br/> **Earliest date available:** 2020-09-08 | C14 | Wave 4, Sept 8, 2020 |
+| `smoothed_wearing_mask` | *Discontinued as of Wave 8, Feb 8, 2021* Estimated percentage of people who wore a mask for most or all of the time while in public in the past 5 days; those not in public in the past 5 days are not counted. <br/> **Earliest date available:** 2020-09-08 | C14 | Wave 4, Sept 8, 2020 |
+| `smoothed_wearing_mask_7d` | Estimated percentage of people who wore a mask for most or all of the time while in public in the past 7 days; those not in public in the past 7 days are not counted. <br/> **Earliest date available:** 2021-02-08 | C14a | Wave 8, Feb 8, 2021 |
 | `smoothed_others_masked` | Estimated percentage of respondents who say that most or all *other* people wear masks, when they are in public and social distancing is not possible <br/> **Earliest date available:** 2020-11-24 | C16 | Wave 5, Nov 24, 2020 |
 | `smoothed_travel_outside_state_5d` | Estimated percentage of respondents who report traveling outside their state in the past 5 days <br/> **Earliest date available:** 2020-04-06 | C6 | Wave 1 |
 | `smoothed_work_outside_home_1d` | Estimated percentage of respondents who worked or went to school outside their home in the past 24 hours <br/> **Earliest date available:** 2020-09-08 | C13 | Wave 4, Sept 8, 2020 |

docs/symptom-survey/coding.md

@@ -467,6 +467,9 @@ new items were meant to capture reasons for vaccine hesitancy among respondents.
   were revised and expanded for clarity. Please review the changes carefully
   when you use responses from multiple waves of this survey, since they may
   shift which occupations respondents choose.
+* C14a is a revision of item C14, changed from "the past 5 days" to "the past
+  7 days" to be consistent with other items on the COVID Symptom Survey.
+  C14a replaces C14.
 
 #### New Items