The author makes no mention of friends. The 90% figure comes from the frequency with which he currently sees his parents and sisters. The title is link-bait-y

The author makes no mention of friends. The 90% figure comes from the frequency with which he currently sees his parents and sisters. The title is link-bait-y, but I think there's actually some substance there: by 30, you've seen 90% of the days you'll spend in person with siblings and parents.