The lesson
Donor Retention is the share of last year's donors who have given again this year. The Donor Retention card on Charity Overview shows yours. It is built from two Behaviour audiences: Retained donors (gave last year and this year) divided by Gave last year. Always divide by last year's donors. They are the people you are trying to keep.
Careful with names: the Donor Retention insight in the Field Guide is something else. It splits one-time donors from repeat donors. It is not a rate.
The Donor Movement chart compares last year with the year before. Lost gave the year before but not last year. Increased, Unchanged and Decreased gave in both years. New and Re-engaged gave last year after a year with no gifts. Read those two bars together: Mission splits them by how long ago each person's first gift was, counted back from today, so last year's brand-new donors can show up in either one.
Donor Value Movement goes one step further: New, Lapsed, Stable, Upgraded and Downgraded, using value bands built from your own giving data. "Higher" means higher for you.