The document discusses the development of a new social media metric called the Semantic Engagement Index (SEI) that aims to more accurately measure sentiment in social media conversations than existing metrics. SEI analyzes tone, emotional affect, and personalization. Case studies show SEI has strong correlations with sales for hospitality and food/beverage clients, with negative sentiment having a greater impact than positive sentiment. Marketing response models incorporating SEI provide insights into how social media conversations impact business and how to optimize marketing spend.