Short Availability

Short availability estimates how many more shares a borrower could still source in the
securities-lending market: the spare part of the lending pool, after the shares already
on loan. The endpoints return two fields:

How it is calculated

Utilization is the share of the lendable pool that is already on loan, so the pool follows
from the shares on loan and utilization:

lendable pool  = shares on loan / utilization
available      = lendable pool − shares on loan  (+ separately advertised broker inventory)

Two adjustments apply:

• The pool is capped at the free float. Insider and strategic holdings do not sit in
  lending programmes, so the pool can never be larger than the shares in public hands. When
  shares on loan reach the free float, availability is zero.
• Broker inventory is added. Shares a prime broker advertises as available, outside the
  agent-lender pool, are added to the spare shares.

What the percentage represents

shortAvailabilityPct measures spare capacity relative to current borrowing. 100%
means another loan as large as all current borrowing could still be sourced. 25% means
borrowing could grow by a quarter before the pool runs dry.

Before the two adjustments, the percentage depends only on utilization:

shortAvailabilityPct = (1 − utilization) / utilization × 100
utilization          = 100 / (100 + shortAvailabilityPct)

So the two measures move in opposite directions. As utilization rises towards 100%,
availability falls towards 0; as utilization falls towards 0, availability grows without
limit.

Where the free-float cap applies, availability is lower than the table suggests; where
broker inventory is added, it is higher.

Why the percentage is bounded

The percentage divides by the shares on loan, so it grows without limit as borrowing
approaches zero. A stock with a large lending pool and almost no borrowing (utilization
of a fraction of a percent) is simply very easy to borrow; the exact multiple carries no
further information.

• The percentage is capped at 9,999%. It reaches the cap when utilization is below about
  1%, or when broker inventory is large relative to the shares on loan. On a typical day
  around a fifth of covered stocks are at the cap, mostly small companies with very little
  borrowing.
• With no shares on loan the percentage is null, since it has no base.
  shortAvailabilityShares is still returned.

Read a value at the cap, or anything in the thousands of percent, as "plentiful, borrowing is
negligible", not as a precise measure.

Change from v1¹

Footnotes

1. Why v1.1 replaces the v1 figure. v1 published the whole lendable pool as
   shortAvailabilityShares, including the shares already on loan. That overstates what a
   borrower can still source by a factor of 1 / (1 − utilization): about 1.4× at 30%
   utilization, 10× at 90%. And at 100% utilization it still reported a pool as large as
   current borrowing where the true answer is zero. v1's percentage already measured spare
   capacity (it equals the formula above), so v1's two fields disagreed with each other; in
   v1.1 the share count matches the percentage. v1 also capped availability at shares
   outstanding minus shares on loan, which counts holders who never lend (index funds, retail)
   and could push the result below zero. v1.1 caps the pool at the free float instead. Both
   versions cap the percentage at 9,999%. Example, AAON on
   2026-10-08: v1 reported 48,271,785 shares; 14.5 million of them were on loan
   (about 30% utilization), so 33,804,824 were still available, which is the v1.1 figure.
   Both versions report the same shortAvailabilityPct, 233.67%: only the share count
   changes. ↩