Analysis
NAICS 52592 is the 2022 NAICS industry for trusts, estates, and agency accounts, part of 5259 (Other Investment Pools and Funds).
It has only one more detailed code, 525920, which covers exactly the same activities; the definition, index entries and statistics are on that page.
County Business Patterns publishes no national count for it, either because the code is out of the survey's scope or because the figures are suppressed to protect individual businesses.
Official definition
See industry description for 525920.
Source: US Census Bureau, NAICS 2022 Manual.