What is Collection year ?
Collection year meaning The academic year in which IPEDS data were collected. Most Institutional Characteristics, Human Resources, Fall Enrollment, and Admissions data are collected for the current year; Completions, 12-Month Enrollment, Student Financial Aid, Academic Libraries and Finance data collections cover the prior year. Graduation Rates and Outcome Measures cover cohorts from prior years that completed college by August 31 of the most recent fall.
reference: IPEDS Data Collectrion System – Glossary