This report describes how we used data from the National Housing Preservation Database (NHPD) to explore the importance of the Low-Income Housing Tax Credit (LIHTC) in The Low-Income Housing Tax Credit: Past Achievements, Future Challenges. It describes the relationship of the NHPD property-level database to the transaction-level database from the US Department of Housing and Urban Development (HUD). Because of both databases’ limitations, we recommend using newer data and validating the NHPD against local sources. Researchers interested in unduplicated unit counts should use the NHPD’s property-level file; those interested in LIHTC transactions should consider using the HUD dataset or the NHPD’s transaction-level file.
This report was updated in September 2018. An earlier version of the report mistakenly stated in several places that HUD’s LIHTC database included each tax credit transaction but that they were not aggregated at the level of the property or address. They are aggregated by property. We have corrected these statements throughout the document. This did not affect any part of our data analysis or findings.