Persistence Factor

What is the straight up formula for persistence factor? And what does it mean? I wrote it down after a long day of studying, can’t read my own writing (its been known to happen sometimes) I’ve been searching the internet and the notes and can’t seem to find it. Any help would be appreciated.

CFA II Chapter 43: Residual Income Valuation High persistence factors are associated with what two things? 1. Low div payouts. 2. Historically high residual income persistence in the industry. Low persistence factors are associated with what three things? 1. High ROE. 2. Significant levels of nonrecurring items. 3. High accounting accruals.