A pure chronological feed fails at scale because it creates incentives for high-volume professional posters to dominate everyone's feed, crowding out less frequent but more meaningful posts from friends and family, and because recency is only one input into relevance, not the only one.

38:53when you scale it up, right? So if you do a pure chronological feed, the incentive for everybody is to just post as much as possible uh because it will always be at the top of everyone who follows you's feed as soon as you post. So what ends up happening is that the feed gets overwhelmed with professional content with usually large company content and publishers because they get,

39:18you know, the New York Times can pump out 50 things a day. your your best friend won't you might get one thing a week from them and so your fee just gets taken over. Um so part of it is the incentives that emerge because when you when you design these systems it's almost like designing a city. You need to think about okay here's the here are the here's how the

39:39mechanics work. What are the incentives that arise? How are people going to act within those incentives? And then what happens? And the other thing is sometimes the most interesting thing was just not the most recent thing. Recency is an important input into relevance, but it's not the only one. My sister got engaged last night and you know she's in Germany. >> No, she didn't. If she did, she's

39:59married. >> She got married last year. That's why it was top of mind. >> All right. >> But if she got engaged, you know, and I missed it because she lives in Europe and you know, we're different time differences. Like, do I really want to see a picture of like my brother's pobo sandwich, you know, poboy sandwich, or do I want to like see my sister's things

40:15first? So, I I It's tough. It's tough. I'd love to figure out a way to find the right balance. I want to give people agency over the experience, but I think it needs to be in a way that creates a system that makes sense, not just for us as a business, which matters. I'm not pretending that's not an issue, but also for the overall community because we've

40:33done chronological by default and where you can make it default and you see not only does usage go down, overall sentiment goes down. the individual who made that choice might be happy at the moment, but when you just get pummeled with stuff you're less interested in over the course of months, we ask, we run surveys at massive scales, we just see people start to become less and less