The claim is strongly supported by the official National Association of REALTORS source, "NAR Existing-Home Sales Report Shows 3.6% Decrease in March," which matches the central figures: a 3.6% decline and a seasonally adjusted annual rate of 3.98 million. Corroboration from the Associated Press article at WTOP repeats the same numbers and explicitly says this marked the slowest pace in nine months, which is consistent with the statement that it was the lowest level since June 2025. The wording about a weaker start to the spring housing market is also supported by the WTOP/AP report.