Trucking capacity is relatively stable while demand is anything but
The question of how trucking capacity is growing or declining is common in industry, but the reality is that demand fluctuations are far more important to monitor as they swing much more violently.
Since December of 2018, the total tractor count from for-hire fleets (non-private) has grown 18%, according to the FMCSA, but has never shown a monthly change of over 2%. By contrast, the Outbound Tender Volume Index (OTVI), a measure of total truckload demand, has grown 12% over the same period, but monthly fluctuations topped 20% at times.
Even before the pandemic, the OTVI had 5-7% monthly swings in demand. Given the OTVI measures total tenders and is not a pure proxy for shipments, it is reflective of how fast demand-side conditions change in trucking.
The point is that capacity shifts are slow and stable, while demand changes much more rapidly and is very unpredictable over time. This is the consummate struggle of supply chains and transportation companies across the globe — how much infrastructure (capacity) is needed to be able to flex up but not have too much overhead when demand softens?