Why concentration changes the advance rate

The same dollar of stock counts for less when it is a large share of the collateral.

Advance rates are usually published as though they depend only on asset type: this much for large-company stock, that much for investment-grade bonds. In practice they also depend on the shape of your particular portfolio, and the mechanism is called a concentration limit.

The idea is straightforward. A lender holding twenty positions can sell them in parallel, and the reasons they might fall are only partly shared. A lender holding one position has a single point of failure: one earnings miss, one regulatory action, one halted stock, and the entire collateral base moves together. The second situation deserves a bigger discount, so concentration rules reduce the advance rate on any holding above a stated share of the account.

Concentration rules commonly appear in a few forms:

A cap: any single position above, say, 25% of the account has its advance rate reduced on the excess.
A cliff: above some share, the excess portion counts for nothing.
A sector or issuer test, so five holdings in the same industry can trip a limit that no single one would.
A special rule for the shares of a company you are employed by or an insider of.

The reason this matters beyond the arithmetic is that concentration is often not something you chose deliberately. A holding that has appreciated for a decade becomes concentrated by winning. Your borrowing capacity can therefore fall as a direct consequence of your best position doing well, which is a genuinely counter-intuitive result worth checking rather than assuming.

Key terms

Concentration limit: A rule reducing the advance rate on positions that exceed a stated share of the pledged account.
Single point of failure: A structure where one event can move the whole collateral base. Lenders price this with lower advance rates.
Blended advance rate: The weighted average advance rate across all pledged holdings, after concentration adjustments.

Worked example

Winning your way into a smaller line

A $1,000,000 account. Base advance rate 65% on large-cap equity, reduced to 30% on any single position's value above 25% of the account.

Diversified: ten $100,000 positions: Lending value $650,000
One position grows to $400,000, others total $600,000: —
First $250,000 of the big position: $162,500
Excess $150,000 of the big position: $45,000
Remaining $600,000: $390,000
New lending value: $597,500

Identical market value, $52,500 less capacity. The position did nothing wrong except get large.

Check yourself

Why would a lender assign a lower advance rate to a $500,000 single-stock account than to a $500,000 twenty-stock account?

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Educational only. Nothing in this lesson is investment, legal or tax advice, or a recommendation to enter into any transaction. Figures are illustrative and computed from the inputs stated in the lesson.