## _wp0613 - References

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---

### I. Introduction
- Contingent credit lines (CCLs) are widely used by banks for commercial and industrial lending and play an important role in short-term capital markets.
- A U.S. Federal Reserve survey shows that over three-quarters of bank lending is done using commitment contracts; as of June 2005, the outstanding (unused) CCLs of U.S. firms were close to $1.72 trillion, more than double that in 1990.
- Pricing and hedging of CCLs has received limited attention; recent advances in financial modeling and new liquid option contracts permit more detailed analysis.
- This paper uses a financial engineering approach to examine the structure of simple CCLs and develops a method for their pricing.
- Typical credit line contract characteristics:
  - Specifies a maximum amount (the commitment) that a bank is committed to lend over a given period; the client can draw any amount up to the maximum.
  - Specifies an interest rate on the drawdown, either fixed or as a spread over a reference rate such as LIBOR.
  - Specifies fees: an upfront commitment fee, an annual fee on the total committed amount, and a usage fee on the undrawn portion.
  - Contains an escape clause or material adverse change (MAC) clause allowing the bank to deny credit if the client’s financial condition changes.
- Company motivations for using lines of credit:
  - Backstop facilities to provide flexibility and avoid borrowing during temporary spikes in commercial paper (CP) rates.
  - Signal of ability to pay for specific transactions, reducing credit risk on short-term borrowing.
  - Reputation effects: opening a credit line with a reputable bank reduces information asymmetries.
- Renewal dynamics:
  - Renewal of credit lines validates credit-worthiness; termination can signal deteriorating financial health.
  - Clients have incentives to roll over existing credit lines with the same banks.
- Organization of paper:
  - Section II discusses the market for CCLs.
  - Section III models a canonical credit line.
  - Section IV provides a replication strategy.
  - Section V proposes two pricing methods and uses Monte Carlo simulations to examine parameter effects.
  - Last section concludes.

### II. Market practice and fees
- Short-term capital market financing types for investment grade borrowers:
  - Syndicated loan market for relatively large issuers.
  - Commercial paper (CP) market for high grade issuers to finance daily operations.
  - CCL facilities or CP backstop loans associated with CP markets and other operations (focus of paper).
- Market size and fee levels:
  - In 2001, total volume of CP backstop facilities in the United States was around $290 billion.
  - Participation fees: banks in syndicates typically paid 1 basis point for every $10 million of the loan they underwrite.
  - Undrawn or facility fees: during 2001 facility fees were in the 8-13 basis point range depending on borrower creditworthiness.
  - Drawn fees (all-in drawn fee over LIBOR):
    - During 2001 this fee averaged 73 basis points and in 2002 the average was 53 basis points.
    - 1-year LIBOR averaged 3.8 percent in 2001 and 2.2 percent in 2002.
  - Term-out fees and maturity choices:
    - Before 2000 most CCLs were multi-year (up to five years); after corporate scandals, 60 percent of CCLs were marketed as one year (364 day) facilities during 2002-2003.
    - Term-out fees were 12.5 basis points in 2001 and increased to 25 basis points in 2002.
  - Some CCLs embed currency options allowing draws in more than one currency; such features are more complex but not necessarily harder to price (ignored in this paper).
- Syndication and regulatory capital treatment:
  - Large CCLs are sold through syndications consisting of banks with close borrower relationships.
  - From the banks’ perspective, as long as the facility is not drawn, a commitment with original maturity of less than one year carries a zero risk-capital weight.
  - For commitments with original maturity greater than one year, banks are required to hold half the capital required for regular loans.

### III. Canonical CCL model and mechanics
- Objective: transfer the risk associated with a low probability event A that may negatively affect a firm’s funding opportunities (e.g., temporary closing of the CP market or a temporary spike in CP rates).
- Canonical contract features:
  - Contract written at time t0 for n periods with maturity T = tn.
  - Maximum loan size $N; model assumes full line is drawn when used.
  - Unused portion subject to a facility fee denoted by u_t0, interpreted here as the CCL premium paid up front at contract initiation.
  - Drawn portion subject to a drawn-fee s_t0 expressed as a spread over LIBOR; fees are fixed at negotiation.
  - Bermudan-type access: CCL can be tapped only at predetermined times t1, t2, ..., t_{n-1}.
  - When drawn at t_i, borrower pays all-in interest r_{t_i} = L_{t_i} + s_t0.
  - Borrower may prepay drawn amount if market credit spread falls below s_t0.
- Modeling simplifications and notes:
  - Assumes full drawdown when facility is used (partial takedowns can be accommodated).
  - Bermudan access dates simplify modeling and replication when t_i − t_{i-1} is small.
  - Participation and term-out fees are ignored.
  - Casual evidence suggests a substantial majority of CCLs are not drawn at all.

### IV. Event B (downgrade) and CCL trigger mechanics
- Event B (downgrade) voids the CCL if it occurs at some time t with 0 < t < T.
- Trigger condition for downgrade: c_t > c.
- Feasibility requirement: c > s_t0.
- All-in interest for short-term borrowing at time t_i:
  - r_{t_i} = L_{t_i} + c_{t_i}
- Borrower draws on CCL at t_i only if market credit spread exceeds all-in drawn fee:
  - c_{t_i} > s_t0 for t0 < t_i
- Loan is repaid when market spread c_{t_i} goes below s_t0.
- If c_{t_i} exceeds c the borrower is downgraded and the CCL becomes void.
- CCLs function as liquidity and credit enhancement; draws are temporary and not intended to result in large permanent bank lending.

### V. Replicating portfolio and valuation structure
- Replication instruments:
  - A cap (collection of caplets) written on the credit spread c_t with cap rate s_t0; caplet payoff at t_{i+1}:
    - Max[N (c_{t_i}   s_t0); 0]
  - A reverse knock-out (barrier) option that knocks out upon the credit event {c_t > c for t0 ≤ t ≤ T}.
- Replicating portfolio = cap on c_t + barrier option that knocks out the cap if {c_t > c} occurs during life of the contract.
- Caplet fair market value at time t (when not knocked out):
  - (cpl)_i^t = B(t; t_{i+1}) E_t[ N  Max(c_{t_i}   s_t0; 0) 1_{c_t < c; t0 ≤ t ≤ t_i} ]
- Cap value at time t: (cap)_t = sum_{i=1}^n (cpl)_i^t
- Heuristic exercise/rollover:
  - If CCL tapped at t_i, corporation pays s_t0 over L_{t_i} for period t_{i+1} − t_i = .
  - At t_{i+1} firm chooses to repay CCL and roll or borrow in CP market if c_{t_{i+1}} < s_t0.
- CCL viewed as a sequence of options on floating-rate loan contracts struck at spread s_t0, each exercised if c_{t_i} > s_t0 and knocked out if c_{t_i} > c.

### VI. Pricing methods and model dynamics
- Corporate credit spread (forward) defined as:
  - c(t; t_i; t_{i+1}) = f(t; t_i; t_{i+1})   F(t; t_i; t_{i+1})
- Method 1 (Schönbucher extension of forward-LIBOR model):
  - Forward LIBOR under t_{i+1}-forward measure: F(t; t_i; t_{i+1}) = E_{P_{t_{i+1}}}[ L_{t_i} ]
  - Under t_2-forward measure (notation F_t and f_t):
    - dF_t = F_t _F_t d! (no drift)
    - df_t = μ(f_t; (t)) dt + f_t _f_t d!(t) (unknown drift under t_2-forward)
  - Using t_2-survival measure (~P_{t_2}) makes f_t a martingale:
    - df_t = f_t _f_t d!(t) under ~P_{t_2}
  - Change-of-measure introduces known drift terms; Wiener processes connected via recursively defined _t^2(t) and _D^t_2(t).
  - Dynamics under t_2-survival measure summarized (as given in text):
    - dF_t = F_t _F_t   d!(t)   _D^t_2(t) dt
    - df_t = f_t _f_t d!(t)
    - dc(t) = F_t _F_t _D^t_2(t) dt + [ f_t _f_t   F_t _F_t ] d!(t)
    - dH(t) = [ F_{t1} + F_t  (1 + H(t)) _D^t_2(t)   H(t) _H_t ] dt + H(t) _H_t d!(t)
  - Single-caplet CCL price expressed as discounted expectation under survival measure:
    - (CCL)_{t_0} = B(t_0; t_2) N  E[ Max(c_{t1}   s_t0; 0) 1_{c_t < c; t0 ≤ t ≤ t1} ]
- Method 2 (risky bond normalization / forward measure ~P_{t_{i+1}}):
  - Real-world dynamics:
    - dF_t = a(F_t; t) dt + _F_t F_t d!^{(1)}_t
    - df_t = b(F_t; f_t; t) dt + _f_t f_t d!^{(2)}_t
    - dc_t = df_t   dF_t
  - Under B(t; t_2) normalization, f_t is a martingale without drift:
    - df_t = _f f_t d~!^{(2)}_t
  - Risk-free forward rate F_t assumed mean-reverting:
    - dF_t = (   F_t) dt + _F F_t d!^{(1)}_t
  - Drift calibration: introduce constant _t, calibrated by matching Black's closed-form caplet price with simulated caplet price.
  - Simulated dynamics after calibration:
    - df_t = _f f_t [  dW^{(1)}_t + sqrt(1   ^2) dW^{(2)}_t ]
    - dF_t = [ (   F_t) +  _F F_t ] dt + _F F_t dW^{(1)}_t
    - Instantaneous correlation: d~!^{(1)}_t d~!^{(2)}_t =  dt

### VII. Simulation setup and key parameter specifications
- Notional sum for simulations: $1
- Common parameter values used in Method 1 simulations:
  - _F = 15%; t_1 = 1; t_2 = 2
  - Initial values: F_{t0} = 6:7%, f_{t0} = 8:3%; c_{t0} = 1:6%
  - Example cap/knock-out parameter: c = 0:055 (illustrated in Figure 3)
- Common parameter values used in Method 2 simulations:
  - _F = _cpl = 15%;  = 0:05;  = 6:5%; t_1 = 1; t_2 = 2
  - Initial values: F_{t0} = 6:7%, f_{t0} = 8:3%; c_{t0} = 1:6%
  - Correlation parameter:  (varied in Figures 6ñ12)
  - Caplet volatility input: _cpl
- Caplet pricing formulas referenced: Black's caplet price (at-the-money) using P(t_0; t_2), N, , F_{t0}, and _cpl.
- Simulation methodology:
  - Euler discretization for forward-rate SDEs.
  - Monte Carlo trajectories for c(t) to compute discounted expected payoff of replicating portfolio.
- Units of reported prices: basis points.

### VIII. Simulation findings and sensitivities
- General relationships:
  - CCL payoff/price increases with higher probability that c_t > s_t0.
  - Higher c_t also raises probability of breaching knock-out barrier c, which dampens CCL payoff.
- Method 1 (Figures 3–5) qualitative findings:
  - CCL payoff is a decreasing function of s_t0 for fixed _f and c.
  - For fixed s_t0, CCL price initially rises with volatility _f and then declines as high _f increases knock-out probability.
  - The _f corresponding to peak CCL price increases with c.
  - Higher c (knock-out threshold) increases CCL price (lower knock-out probability).
  - Example parameter points shown in figures:
    - c = 0:055 (Figure 3)
    - s_t0 = 0:025 (Figure 4)
    - _f = 0:025 (Figure 5)
- Method 2 (Figures 6–12) qualitative findings:
  - Graphs similar to Method 1 but shifted up by a few basis points.
  - Sensitivity to correlation :
    - For fixed  and increasing _f, CCL price first increases then decreases (knock-out effect).
    - Higher  tends to reduce volatility of c_t and thus generally lowers CCL price, but for high _f higher  can attenuate knock-out probability and potentially make CCL price positively related to .
    - Relationship between CCL price and  depends on relative sizes of c and s_t0:
      - If c is large relative to s_t0 (e.g., c = 0:08; s_t0 = 0:025) relationship between  and CCL price is clearly negative.
      - If c is small relative to s_t0 (e.g., c = 0:04; s_t0 = 0:025) curves are almost flat; small positive slope at high .
    - Figure 12 illustrates potential large pricing errors if  is misspecified; _f series shown: 0.10, 0.15, 0.20, 0.30, 0.40, 0.50.
- Prices in figures reported in basis points.

### IX. Hedging issues and practical constraints
- Two major hedging difficulties:
  1. Reverse knock-out options are hard to hedge, especially near expiration: delta can change sign (positive to negative) as credit spread approaches barrier; option writer faces rapidly changing hedging needs.
  2. Hedging a credit-spread knock-out may require trading complex portfolios of credit default swaps (CDS), including forward default-swap exposures; CDS markets may be illiquid and CDS contracts are relatively expensive.
- Practical consequences:
  - Market makers may treat reverse knock-out option books as unhedgeable and manage via diversification (similar to insurers).
  - Secondary market limitations:
    - Funding obligations are continual due to prepayment options on drawn loans.
    - CCLs cannot be sold without borrower consent; secondary market illiquidity.
  - Hedging via CDS is costly and may send negative signals about borrower credit (purchase of CDS by the lender could harm the borrower), hence not widely used.
- Banks typically manage CCL portfolios as unhedgeable risks and rely on diversification and loan-portfolio management techniques.

### X. Conclusions and extensions
- CCLs can be replicated by a cap on the firm's credit spread composed of caplets that are reverse knock-out options.
- Pricing CCLs is more complex than pricing standard options because credit lines can be partially exercised and include knock-out features.
- Hedging CCLs is costly and difficult; banks often treat CCL portfolios as unhedgeable and rely on diversification.
- Possible extensions to the CCL structure:
  - Add a term-out option.
  - Model explicitly the pre-payment of loans drawn under the credit line for longer-term CCLs.

*Source: Excerpt from _wp0613 - References (PDF content provided).*

### References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   24

### _wp0613 - References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   24

### I. Introduction
- Contingent credit lines (CCLs) are widely used by banks for commercial and industrial lending and play an important role in short-term capital markets.
- A U.S. Federal Reserve survey shows that over three-quarters of bank lending is done using commitment contracts, and as of June 2005, the outstanding (unused) CCLs of U.S. firms were close to $1.72 trillion, more than double that in 1990.
- Pricing and hedging of CCLs has received limited attention in the finance literature; recent advances in financial modeling and new liquid option contracts permit more detailed analysis.
- This paper uses a financial engineering approach to examine the structure of simple CCLs and develops a method for their pricing.
- Typical credit line contract characteristics:
  - Specifies a maximum amount (the commitment) that a bank is committed to lend over a given period; the client can draw any amount up to the maximum.
  - Specifies an interest rate on the drawdown, either fixed or as a spread over a reference rate such as LIBOR.
  - Specifies fees: an upfront commitment fee, an annual fee on the total committed amount, and a usage fee on the undrawn portion.
  - Contains an escape clause or material adverse change (MAC) clause allowing the bank to deny credit if the client’s financial condition changes.
- Company motivations for using lines of credit:
  - Backstop facilities to provide flexibility and avoid borrowing during temporary spikes in commercial paper (CP) rates.
  - Signal of ability to pay for specific transactions, reducing credit risk on short-term borrowing.
  - Reputation effects: opening a credit line with a reputable bank reduces information asymmetries.
- Renewal dynamics:
  - Renewal of credit lines validates credit-worthiness; termination can signal deteriorating financial health.
  - Clients have incentives to roll over existing credit lines with the same banks.
- Relevant literature and precedents:
  - Mozebach (1999): banks often have considerable access to corporate information; granting a line signals firm viability and produces a positive market reaction on the protection buyer’s stock.
  - Calomiris (1989): bank loan commitments backing commercial paper provide insurance against systemic liquidity risk; CP back-stops function as a source of funds during extreme CP market volatility.
  - Early option-pricing approach to loan commitments: Thakor, Hong and Greenbaum (1981).
- Paper organization:
  - Section II discusses the market for CCLs.
  - Section III models a canonical credit line.
  - Section IV provides a replication strategy.
  - Section V proposes two pricing methods and uses Monte Carlo simulations to examine parameter effects.
  - Last section concludes.

### II. Market Practice
- Short-term capital market financing types for investment grade borrowers:
  - Syndicated loan market for relatively large issuers.
  - Commercial paper (CP) market for high grade issuers to finance daily operations.
  - CCL facilities or CP backstop loans associated with CP markets and other operations (focus of paper).
- Market size and fees:
  - In 2001, total volume of CP backstop facilities in the United States was around $290 billion.
  - Participation fees: banks in syndicates typically paid 1 basis point for every $10 million of the loan they underwrite.
  - Undrawn or facility fees: during 2001 facility fees were in the 8-13 basis point range depending on borrower creditworthiness.
  - Drawn fees (major component): expressed as an all-in drawn fee (total funding cost over LIBOR paid by a borrower who avails of the CCL).
    - During 2001 this fee averaged 73 basis points and in 2002 the average was 53 basis points.
    - 1-year LIBOR averaged 3.8 percent in 2001 and 2.2 percent in 2002.
  - Term-out fees: before 2000 most CCLs were multi-year (up to five years); after corporate scandals, 60 percent of CCLs were marketed as one year (364 day) facilities during 2002-2003.
    - Term-out fees were 12.5 basis points in 2001 and increased to 25 basis points in 2002.
  - Some CCLs embed currency options allowing draws in more than one currency; these are more complex but not necessarily harder to price (ignored in this paper).
- Syndication and regulatory capital treatment:
  - Large CCLs are sold through syndications consisting of banks with close borrower relationships.
  - From the banks’ perspective, as long as the facility is not drawn, a commitment with original maturity of less than one year carries a zero risk-capital weight—hence preference for maturities less than a year.
  - For commitments with original maturity greater than one year, banks are required to hold half the capital required for regular loans.

### III. Modeling a CCL
- Objective: transfer the risk associated with a low probability event A that may negatively affect a firm’s funding opportunities (e.g., temporary closing of the CP market or a temporary spike in CP rates).
- CCL contract features (canonical model):
  - Contract written at time t0 for n periods (months or years) with maturity T = tn.
  - Maximum loan size $N; borrower can draw any amount up to $N. The model assumes the full line is drawn when used to simplify replication.
  - Unused portion subject to a facility fee denoted by u_t0, interpreted here as the CCL premium paid up front at contract initiation (different from market practice where u_t0 is paid as an annual fee over the contract).
  - Drawn portion subject to a drawn-fee s_t0 expressed as a spread over LIBOR; fees have subscript t0 as they are decided at negotiation and remain constant.
  - Contract is Bermudan-type: the CCL can be tapped only at predetermined times t1, t2, ..., t_{n-1} (simplification; in practice access may be at any time).
  - When the credit line is drawn at time t_i (i = 1,2,..., n-1), the borrower pays the annual all-in interest cost r_{t_i} = L_{t_i} + s_t0.
  - The borrower has the option to prepay the amount drawn; if the firm’s credit spread in the CP market falls below s_t0, the firm will choose to repay the bank.
- Modeling simplifications and notes:
  - Assumes full drawdown when facility is used (can be relaxed for partial takedowns).
  - Bermudan access dates simplify modeling and replication when t_i - t_{i-1} is small.
  - Participation and term-out fees are ignored for simplicity.
  - Reliable empirical data on proportion of amount committed under CCLs actually drawn is not available; casual evidence suggests a substantial majority of CCLs are not drawn at all.

*Source: Excerpt from _wp0613 - References . . . . . . . . . . . . . . . . . . . . . . . . . .   24*

### 7. If an eventBoccurs at some datet,t

### _wp0613 - 7. If an eventBoccurs at some datet,t

### CCL structure and mechanics
- Event B (downgrade) voids the CCL if it occurs at some time t with 0 < t < T.
- Trigger condition for downgrade: c_t > c.
- Feasibility requirement: c > s_t0.
- All-in interest for short-term borrowing at time t_i:
  - r_ti = L_ti + c_ti
- Firm draws on CCL at t_i only if market credit spread exceeds all-in drawn fee:
  - c_ti > s_t0 for t0 < t_i
- Loan is repaid when market spread c_ti goes below s_t0, ensuring the temporary nature of CCL draws.
- If c_ti exceeds c the borrower is downgraded and the CCL becomes void.
- CCLs function as liquidity and credit enhancement; draws are meant to be temporary and the facility is not intended to result in large permanent bank lending.

### Replicating portfolio for a CCL
- Replication instruments:
  - A cap (collection of caplets) written on the credit spread c_t with cap rate s_t0; caplet payoff at t_i+1:
    - Max[N (c_ti   s_t0); 0]
  - A reverse knock-out (barrier) option that knocks out upon the credit event:
    - c_t > c for t0 ≤ t ≤ T
- Replicating portfolio = cap on c_t + barrier option that knocks out the cap if {c_t > c} occurs during life of the contract.
- Caplet fair market value at time t (when not knocked out) includes indicator that borrower is not downgraded before caplet expiry:
  - (cpl)_i^t = B(t; t_i+1) E_t[ N  Max(c_ti   s_t0; 0) 1_{c_t < c; t0 ≤ t ≤ t_i} ]
- Cap value at time t: (cap)_t = sum_{i=1}^n (cpl)_i^t
- Heuristic exercise/rollover description:
  - If CCL tapped at t_i, corporation pays s_t0 over L_ti for period t_{i+1} − t_i = .
  - At t_{i+1} firm chooses to repay CCL and roll or borrow in CP market if c_{t_{i+1}} < s_t0.
- CCL can be seen as a sequence of options on floating-rate loan contracts struck at spread s_t0, each option exercised if c_ti > s_t0 and knocked out if c_ti > c.

### Pricing: modeling dynamics and valuation
- Corporate credit spread (forward) defined as:
  - c(t; t_i; t_{i+1}) = f(t; t_i; t_{i+1})   F(t; t_i; t_{i+1})
- Two modeling methods presented.

- Method 1 (Schönbucher extension of forward-LIBOR model):
  - Forward LIBOR under t_{i+1}-forward measure: F(t; t_i; t_{i+1}) = E_{P_{t_{i+1}}}[ L_{t_i} ]
  - Under t_2-forward measure (notation simplification F_t and f_t):
    - dF_t = F_t _F_t d! (no drift)
    - df_t = μ(f_t; (t)) dt + f_t _f_t d!(t) (unknown drift under t_2-forward)
  - Using t_2-survival measure (~P_{t_2}) makes f_t a martingale:
    - df_t = f_t _f_t d!(t) under ~P_{t_2}
  - Change-of-measure relationships introduce known drift terms; Wiener processes connected via recursively defined _t^2(t) and _D^t_2(t) (see text).
  - Dynamics under single measure (t_2-survival measure) summarized:
    - dF_t = F_t _F_t   d!(t)   _D^t_2(t) dt
    - df_t = f_t _f_t d!(t)
    - dc(t) = F_t _F_t _D^t_2(t) dt + [ f_t _f_t   F_t _F_t ] d!(t)
    - dH(t) = [ F_{t1} + F_t  (1 + H(t)) _D^t_2(t)   H(t) _H_t ] dt + H(t) _H_t d!(t)
  - CCL price (single-caplet case) expressed as discounted expectation under survival measure:
    - (CCL)_{t_0} = B(t_0; t_2) N  E[ Max(c_{t1}   s_t0; 0) 1_{c_t < c; t0 ≤ t ≤ t1} ]

- Method 2 (risky bond normalization / forward measure ~P_{t_{i+1}}):
  - Real-world dynamics specified:
    - dF_t = a(F_t; t) dt + _F_t F_t d!^{(1)}_t
    - df_t = b(F_t; f_t; t) dt + _f_t f_t d!^{(2)}_t
    - dc_t = df_t   dF_t
  - Under B(t; t_2) normalization, f_t is a martingale without drift:
    - df_t = _f f_t d~!^{(2)}_t
  - Risk-free forward rate F_t assumed mean-reverting:
    - dF_t = (   F_t) dt + _F F_t d!^{(1)}_t
  - Drift calibration: introduce constant _t, calibrated by matching Black's closed-form caplet price with simulated caplet price.
  - Simulated dynamics after calibration:
    - df_t = _f f_t [  dW^{(1)}_t + sqrt(1   ^2) dW^{(2)}_t ]
    - dF_t = [ (   F_t) +  _F F_t ] dt + _F F_t dW^{(1)}_t
    - Instantaneous correlation between driver Wiener processes: d~!^{(1)}_t d~!^{(2)}_t =  dt

### Simulation setup and key parameter specifications (as used in the paper)
- Notional sum for simulations: $1
- Common parameter values used in Method 1 simulations:
  - _F = 15%; t_1 = 1; t_2 = 2
  - Initial values: F_t0 = 6:7%, f_t0 = 8:3%; c_t0 = 1:6%
  - Example cap/knock-out parameter: c = 0:055 (illustrated in Figure 3)
- Common parameter values used in Method 2 simulations:
  - _F = _cpl = 15%;  = 0:05;  = 6:5%; t_1 = 1; t_2 = 2
  - Initial values: F_t0 = 6:7%, f_t0 = 8:3%; c_t0 = 1:6%
  - Correlation parameter:  (varied in Figures 6ñ12)
  - Caplet volatility input: _cpl
- Caplet pricing formulas referenced:
  - Black's caplet price (at-the-money) using P(t_0; t_2), N, , F_t0, and _cpl (see text for explicit formula).
- Simulation methodology:
  - Euler discretization for forward-rate SDEs.
  - Monte Carlo trajectories for c(t) to compute discounted expected payoff of replicating portfolio.

### Simulation findings and sensitivity results (qualitative and numeric parameter points preserved)
- General relationships:
  - CCL payoff/price increases with higher probability that c_t > s_t0.
  - Higher c_t also raises probability of breaching knock-out barrier c, which dampens CCL payoff.
- From Method 1 (Figures 3–5):
  - CCL payoff is a decreasing function of s_t0 for fixed _f and c.
  - For fixed s_t0, CCL price initially rises with volatility _f and then declines as high _f increases knock-out probability.
  - The _f corresponding to peak CCL price increases with c.
  - Higher c (knock-out threshold) increases CCL price (lower knock-out probability).
- Example parameter points shown in figures:
  - c = 0:055 (Figure 3)
  - s_t0 = 0:025 (Figure 4)
  - _f = 0:025 (Figure 5)
- From Method 2 (Figures 6–12):
  - Graphs similar to Method 1 but shifted up by a few basis points.
  - Sensitivity to correlation :
    - For fixed  and increasing _f, CCL price first increases then decreases (knock-out effect).
    - Higher  tends to reduce volatility of c_t and thus generally lowers CCL price (negative relationship), but:
      - For high _f, higher  can attenuate knock-out probability and potentially make CCL price positively related to .
    - Relationship between CCL price and  depends on relative sizes of c and s_t0:
      - If c is large relative to s_t0 (e.g., c = 0:08; s_t0 = 0:025) relationship between  and CCL price is clearly negative.
      - If c is small relative to s_t0 (e.g., c = 0:04; s_t0 = 0:025) curves are almost flat; small positive slope at high .
  - Figure 12 illustrates potential large pricing errors if  is misspecified; plotted CCL price vs  for multiple _f values:
    - _f series shown: 0.10, 0.15, 0.20, 0.30, 0.40, 0.50 (as labeled in figure caption)
- Units of reported prices: basis points (figures display CCL price in basis points).

### Hedging issues and practical constraints
- Two major hedging difficulties:
  1. Reverse knock-out options are hard to hedge, especially near expiration: delta can change sign (positive to negative) as credit spread approaches barrier; option writer faces rapidly changing hedging needs.
  2. Hedging a credit-spread knock-out may require trading complex portfolios of credit default swaps (CDS), including forward default-swap exposures; CDS markets may be illiquid and CDS contracts are relatively expensive.
- Practical consequences:
  - Market makers may treat reverse knock-out option books as unhedgeable and manage via diversification (similar to insurers).
  - Secondary market limitations:
    - Funding obligations are continual due to prepayment options on drawn loans.
    - CCLs cannot be sold without borrower consent; secondary market illiquidity.
  - Hedging via CDS is costly and may send negative signals about borrower credit (purchase of CDS by the lender could harm the borrower), hence not widely used.
- Banks typically manage CCL portfolios as unhedgeable risks and rely on diversification and loan-portfolio management techniques.

### Conclusions and extensions
- CCLs can be replicated by a cap on the firm's credit spread composed of caplets that are reverse knock-out options.
- Pricing CCLs is more complex than pricing standard options because credit lines can be partially exercised and include knock-out features.
- Hedging CCLs is costly and difficult; banks often treat CCL portfolios as unhedgeable and rely on diversification.
- Possible extensions to the CCL structure:
  - Add a term-out option.
  - Model explicitly the pre-payment of loans drawn under the credit line for longer-term CCLs.

*Source: _wp0613 - 7. If an eventBoccurs at some datet,t (PDF content provided).*

### References

### _wp0613 - References

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*Source: _wp0613 - References*

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