Worked case · Failure and stress · 12 figures

Limits on a changing exposure stock

Use limits to bound exposure

Figure 01 / 12

Separate probability, severity, and exposure

Separate probability, severity, and exposure — Limits on a changing exposure stock. One-year synthetic credit case. Exact values are in the figure data below.
One-year synthetic credit case

The simplified one-year expected loss is PD × LGD × EAD = $73,673.60. PD is 9.20%, LGD is 71.50%, and EAD is $1,120,000. This is a teaching expected-value calculation, not an accounting allowance method or a capital standard.

Figure data and text version
InputValueUnit
PD9.2Percent over one year
LGD71.5Percent of exposure lost conditional on default
EAD1,120,000USD at default
Expected loss73,673.6USD over the stated horizon

A processing limit controls one source of new exposure, while existing obligations continue to mature. The limit needs the right aggregation key and observation period.

Several related accounts each receive the full limit despite one shared loss driver.

All amounts, rates, capacity limits, and outcomes in this case are synthetic. The three conditions are separate assumptions for comparison. A better result in the response condition is not measured proof that the proposed control causes that improvement. The figures expose the calculation and its limits; a real deployment needs its own evidence.

Read the result

The case has $1,120,000 of exposure. Its stated one-year PD and LGD imply $73,673.60 of expected loss, while the cover analysis leaves $812,500.00 of stress exposure. Monthly cash coverage is 0.82×. These are separate measures: one describes an average under probability assumptions, one describes available cover, and one describes a period’s funding capacity.

Model inputs and calculated values

Inputs below are the case-specific values. Each figure states the condition-specific assumptions and units used in its calculation. Calculated values are rounded for display.

InputValue
exposure1,120,000
collateral250,000
reserve170,000
pd0.04
cash65,000
debtService49,000
Calculated valueResult
ead1,120,000
pd0.092
lgd0.715
expectedLoss73,673.6
eligibleCover137,500
reserve170,000
uncovered812,500
cash40,300
debt49,000
dscr0.8224
Figure 02 / 12

Probability and severity move the result together

Probability and severity move the result together — Limits on a changing exposure stock. USD expected loss; fixed exposure. Exact values are in the figure data below.
USD expected loss; fixed exposure

Each cell is the same exposure multiplied by the row default probability and the column loss severity. The grid makes joint stress visible. A downturn can affect both factors; the calculation does not assume that the two causes are independent.

Figure data and text version
PDLGD 25%LGD 50%LGD 75%
2%5,60011,20016,800
5%14,00028,00042,000
10%28,00056,00084,000
20%56,000112,000168,000
Figure 03 / 12

Recorded collateral and eligible cover

Recorded collateral and eligible cover — Limits on a changing exposure stock. USD; some measures overlap. Exact values are in the figure data below.
USD; some measures overlap

The collateral record is $250,000, but a 45% illustrative haircut leaves $137,500.00 eligible in this scenario. Reserve cover adds $170,000. The resulting uncovered exposure is $812,500.00. Eligibility also needs enforceability and operational access; this arithmetic does not establish either.

Figure data and text version
MeasureUSD
Recorded collateral250,000
Eligible collateral137,500
Recorded reserve170,000
Combined usable cover307,500
Uncovered exposure812,500
Figure 04 / 12

Cash available for the period’s debt service

Cash available for the period’s debt service — Limits on a changing exposure stock. USD for one month. Exact values are in the figure data below.
USD for one month

Defined cash available is $40,300.00 against $49,000.00 of debt service, for a 0.82× ratio. The ratio uses one period and one defined cash measure. It does not establish affordability, suitability, or a required underwriting threshold.

Figure data and text version
ComponentUSDMeaning
Cash available40,300After the expenses included in this illustration
Debt service49,000Principal and interest due in the same period
Cash after debt service-8,700Negative means a modeled shortfall
Figure 05 / 12

A constant-hazard illustration

A constant-hazard illustration — Limits on a changing exposure stock. Percent of an initial synthetic cohort. Exact values are in the figure data below.
Percent of an initial synthetic cohort

The curve converts the stated one-year PD of 9.20% to a constant monthly hazard using h = 1 − (1 − PD)^(1/12). Survival after 12 months is therefore 1 − PD. Constant hazard is an assumption; seasonality and changing exposure are omitted. Horizontal positions are the labeled observations or scenarios; equal spacing does not imply equal numerical increments.

Figure data and text version
Months since startSurvival %
M0100
M298.4
M496.83
M695.29
M893.77
M1092.27
M1290.8
Figure 06 / 12

Cumulative expected loss at comparable age

Cumulative expected loss at comparable age — Limits on a changing exposure stock. Cumulative expected USD; fixed exposure. Exact values are in the figure data below.
Cumulative expected USD; fixed exposure

This curve multiplies cumulative modeled default probability by a fixed EAD and LGD. It is useful for separating observation age from the chosen assumptions. It omits amortization, recoveries over time, prepayment, and changing utilization. Horizontal positions are the labeled observations or scenarios; equal spacing does not imply equal numerical increments.

Figure data and text version
AgeExpected USD
M00
M212,777.95
M425,352
M637,725.42
M849,901.4
M1061,883.09
M1273,673.6
Figure 07 / 12

Expected loss sensitivity to PD

Expected loss sensitivity to PD — Limits on a changing exposure stock. USD; LGD and EAD held fixed. Exact values are in the figure data below.
USD; LGD and EAD held fixed

Exposure stays at $1,120,000 and LGD stays at 71.50% while PD changes. The linear relationship follows the simplified expected-loss formula. It is not evidence that real-world losses respond linearly to economic stress. Horizontal positions are the labeled observations or scenarios; equal spacing does not imply equal numerical increments.

Figure data and text version
One-year PDExpected USD
1%8,008
3%24,024
5%40,040
8%64,064
12%96,096
20%160,160
Figure 08 / 12

A shared dependency can dominate exposure

A shared dependency can dominate exposure — Limits on a changing exposure stock. USD; buckets sum to total exposure. Exact values are in the figure data below.
USD; buckets sum to total exposure

The four amounts are disjoint portions of this case’s exposure. The largest bucket represents one shared supplier, funding source, or other specified dependency. Counting customers alone would not reveal this common loss driver.

Figure data and text version
Dependency bucketExposure USD
related merchant group — primary448,000
Independent group B336,000
Independent group C224,000
Independent group D112,000
Figure 09 / 12

A weak month can disappear inside an average

A weak month can disappear inside an average — Limits on a changing exposure stock. USD per month. Exact values are in the figure data below.
USD per month

The six-month path applies explicit seasonal factors to the defined monthly cash amount and compares it with fixed debt service. These are constructed cash assumptions, not a forecast. A negative month needs a funding or terms response even when the average ratio looks comfortable. Horizontal positions are the labeled observations or scenarios; equal spacing does not imply equal numerical increments.

Figure data and text version
MonthCash availableDebt service
M128,21049,000
M234,25549,000
M344,33049,000
M436,27049,000
M552,39049,000
M646,34549,000
Figure 10 / 12

Terms belong in the decision record

Terms belong in the decision record — Limits on a changing exposure stock. Synthetic underwriting record. Exact values are in the figure data below.
Synthetic underwriting record

This record concerns use limits to bound exposure. A binary approval omits the amount, observation horizon, cover assumptions, and review trigger. Retaining those terms makes the decision reproducible and identifies when changed facts require another assessment.

Figure data and text version
FieldIllustrative value
entityLimits on a changing exposure stock
exposure_usd1,120,000
horizonOne year for PD; one month for cash coverage
pd_percent9.2
lgd_percent71.5
review_triggerSeveral related accounts each receive the full limit despite one shared loss driver.
Figure 11 / 12

One cause can affect several loss components

One cause can affect several loss components — Limits on a changing exposure stock. Scenario logic. Exact values are in the figure data below.
Scenario logic

The stress path connects related merchant group to repayment cash, default probability, recovery, and funding needs. Arrows state the scenario’s assumed causal chain. They are hypotheses to test with evidence, not proof that every affected customer will default.

Figure data and text version
StageMechanism
Dependency shockSeveral related accounts each receive the full limit despite one shared loss driver.
Cash pressureReceipts fall or essential payments move earlier
Default and severityRepayment probability and recovery can both worsen
ResponseReassess terms, usable cover, and exposure within the approved process
Figure 12 / 12

Expected loss, uncovered exposure, and cash gap

Expected loss, uncovered exposure, and cash gap — Limits on a changing exposure stock. USD; distinct horizons and meanings. Exact values are in the figure data below.
USD; distinct horizons and meanings

Expected loss ($73,673.60), uncovered exposure ($812,500.00), and monthly cash gap ($8,700.00) answer different questions. The bars are deliberately separated measures and must not be added. A low expected value can coexist with a large stress exposure.

Figure data and text version
MeasureUSD
Expected one-year loss73,673.6
Uncovered stress exposure812,500
Monthly cash gap8,700

Connect the result to the system

Aggregate relevant exposure and enforce reservations before new commitments are accepted.

Check the population, evidence, permitted action, and actual effect together. A balanced calculation can still use the wrong population; a successful response can still leave an unknown financial outcome. The case’s numerical result applies only to its stated assumptions.

Sources and further reading

The chapter sources support the concepts and scope. They do not prescribe the synthetic model rates.

  1. OCC Comptroller’s Handbook: merchant processing
  2. OCC Comptroller’s Handbook: rating credit risk