* General: "The distance decay effect explains why people are more likely to visit businesses closer to home than those further away."
* Specific example: "The distance decay of social media influence is evident in the declining engagement of a local community group as members move further away."
* With an academic tone: "Our research investigated the relationship between distance decay and consumer preferences for local products, finding a strong correlation."
* Informal: "The distance decay of my motivation to clean my room is real – the further away I am, the less likely I am to do it!"
The specific usage will depend on the context and the point you're trying to make.