Update social gain readme.md

Author: mackgalante

vignettes/social_gain_vignette/readme.md

@@ -35,6 +35,8 @@ Fahad, an attending pediatric anesthesiologist at Max Community Hospital, has th
 |Mar  |              97%|               95|          86|
 
 ## Preference data
+Preferences for precision feedback are elicited through a preference survey that providers can take. The preference survey produces a preference model for each provider that, with the provider's permission, is shared with MPOG to maintain. MPOG analyses preference data that is shared to identify population-level preference segments. These segments are generated as preference profiles that can serve as a default preference model for an organization, or which can be selected by providers who do not take the preference survey, but who identify preferences that are close enough to their own in the settings menu for the precision feedback system.
+
 Chikondi's preference data:
 
 |Motivating information |Utility value|Description                                                                     |