The dataset's assignee ranking covers 100 companies, and the leading assignee holds 127 records, with fifth place at 61 and tenth place at 49. The top 5 assignees combined account for 19.9% of all 2,225 records in scope, and the top 10 for 32.2% — meaningful concentration at the very top, but the majority of records belong to a long tail of smaller filers. A freedom-to-operate review should not stop at the largest names.

Filings peaked at 131 in 2023 after running around 106-127 per year earlier in the period, then eased to 60 by 2024, a complete and comparable year showing a 43% drop from 2021. Figures for 2025 and 2026 look lower still, but publication typically lags filing by about 18 months, so those recent years are undercounted and should not be read as a continuing decline. The honest read is a post-2023 pullback of uncertain slope, not a confirmed multi-year collapse.

Resistor technology (IPC class H01C) and protective circuit arrangements (H02H) each appear in roughly 40% of the 2,225 records, making them the densest claim territory, with spark gap and arc devices (H01T) close behind at 29.7%. Switches and relays (H01H) sit at 14.3%, and measurement, power supply/grid, connectors and power conversion classes each fall under 5%. Because a single record can carry multiple IPC classes, these shares add up to more than 100% and should be read individually against the full record count, not against each other as parts of a whole.

US4908730A, assigned to Kearney, claims a modular metal oxide varistor arrester with a coaxial shunt gap formed inside the disk by inward-projecting electrode plates, suited to sealed under-oil use or as a housed component. It is a 1990 grant, so its core disk-and-gap geometry is long since open prior art rather than a live blocking reference, but it illustrates the kind of physical shunt-gap claim that later coordination-of-stages and end-of-life detection patents had to design around. Anyone filing new disk-geometry or gap-placement claims should check it and its citing family regardless of its age.

The thinnest-claimed IPC classes in this dataset are power conversion (H02M, 3.2% of records) and connectors and current collectors (H01R, 3.5%), well below the roughly 40% density in the core resistor and protective-circuit classes. Sub-areas such as follow-current interruption in DC microgrid contexts, end-of-life indication for varistor disks, and connector-integrated surge protection show comparatively light filing activity. High density elsewhere means the claim space for varistor and gas-discharge-tube geometry is occupied, not that the underlying technology is finished — but new claims there will need a clear point of novelty against a crowded field.