This chart reflects fluctuations in the RSJI average over 120 days. Those valleys? Nearly all of them are Sundays. The most recent dip (all the way to the right, a record low RSJI average of 39) was Easter.
Week after week, the RSJI shows the same pattern: a build-up of engagement (#socialjuice) during the week, beginning Monday, and then a falling off over the weekend, with the deepest dips in social engagement happening on Sundays.