Interest Rate Swaps - Fundamentals › Why Use Interest Rate Swaps?
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Swaps serve multiple purposes in financial markets, ranging from hedging to speculation to balance sheet management. Understanding these motivations helps explain why the swap market grew so large.
Hedging Interest Rate Risk
Consider a company that has issued floating-rate debt and wants to lock in its borrowing costs. Perhaps the company has $200 million in bank loans tied to SOFR plus a credit spread. If interest rates rise, the company's interest expense increases, potentially straining cash flow.
By entering a pay-fixed, receive-floating swap with a notional of $200 million, the company effectively converts its floating-rate exposure to fixed. The floating payments received from the swap offset the floating payments on the loan, leaving only the fixed swap rate as the effective borrowing cost.
import numpy as np
import pandas as pd
# Hedging example
loan_notional = 200_000_000
loan_spread = 0.0150 # 150 basis points over SOFR
swap_fixed_rate = 0.0400
# Scenario analysis: What if SOFR varies?
sofr_scenarios = np.linspace(0.02, 0.07, 6) # 2% to 7%
results = []
for sofr in sofr_scenarios:
# Without hedge: floating loan payment
loan_rate = sofr + loan_spread
unhedged_cost = loan_notional * loan_rate
# With hedge: loan payment + swap net
loan_payment = loan_notional * loan_rate
swap_net = loan_notional * (
swap_fixed_rate - sofr
) # Pay fixed, receive floating
hedged_cost = loan_payment + swap_net # = notional * (fixed_rate + spread)
results.append(
{
"SOFR": f"{sofr * 100:.1f}%",
"Unhedged Cost": unhedged_cost,
"Hedged Cost": hedged_cost,
"Savings": unhedged_cost - hedged_cost,
}
)
hedge_df = pd.DataFrame(results)Interest Rate Hedging Analysis Loan: $200M at SOFR + 2 bps Swap: Pay 4% fixed, receive SOFR ------------------------------------------------------------ SOFR Unhedged Cost Hedged Cost Savings 2.0% $7.00M $11.00M $-4.00M 3.0% $9.00M $11.00M $-2.00M 4.0% $11.00M $11.00M $0.00M 5.0% $13.00M $11.00M $2.00M 6.0% $15.00M $11.00M $4.00M 7.0% $17.00M $11.00M $6.00M ------------------------------------------------------------ Hedged cost is always: $11.00M
The analysis demonstrates the hedging power of swaps. Regardless of where SOFR moves, the hedged cost remains constant at the swap fixed rate plus the loan spread. When rates rise above expectations, the company saves money compared to the unhedged position. When rates fall, the company forgoes potential savings but has certainty about its costs.
Asset-Liability Management
Banks face a structural challenge: their deposits (liabilities) typically have short maturities and floating rates, while their loans (assets) often have longer maturities and fixed rates. This creates interest rate risk. If short-term rates rise, the bank's funding costs increase while its loan income stays fixed.
Swaps allow banks to manage this mismatch. A bank can enter pay-floating, receive-fixed swaps to better match its asset and liability characteristics. The fixed swap payments received help offset the fixed income from loans, while the floating payments made are funded by floating-rate deposits.
Comparative Advantage and Cost Reduction
The theoretical foundation for swaps rests partly on the principle of comparative advantage, familiar from international trade theory. Different borrowers face different credit spreads in fixed versus floating markets. A borrower may have an absolute advantage in one market (lower rates than competitors) but a comparative advantage in another (a relatively smaller disadvantage). When parties exploit these comparative advantages through swaps, both can benefit.
Suppose Company A can borrow at 5.0% fixed or SOFR + 0.5%, while Company B can borrow at 6.5% fixed or SOFR + 1.0%. Company A has an absolute advantage in both markets (lower rates in each), but the advantage is larger in the fixed market (150 basis points) than in the floating market (50 basis points). This difference in relative advantages creates an opportunity for mutually beneficial exchange.
# Comparative advantage example
company_a = {"fixed": 0.050, "floating_spread": 0.005} # 5.0% or SOFR + 0.5%
company_b = {"fixed": 0.065, "floating_spread": 0.010} # 6.5% or SOFR + 1.0%
# Differences in borrowing costs
fixed_diff = company_b["fixed"] - company_a["fixed"] # 1.5%
floating_diff = (
company_b["floating_spread"] - company_a["floating_spread"]
) # 0.5%
# Total potential gain from swap
total_gain = fixed_diff - floating_diff # 1.0%
# If A wants floating and B wants fixed, they can both benefit
# A borrows fixed at 5.0%, B borrows floating at SOFR + 1.0%
# They swap: A pays SOFR to B, B pays 5.4% to A (for example)
swap_rate_a_receives = 0.054 # A receives 5.4% from B
# A's net: pays 5.0% to market, receives 5.4% from B, pays SOFR to B
# A's effective rate: 5.0% - 5.4% + SOFR = SOFR - 0.4%
# Without swap, A would pay SOFR + 0.5%, so A saves 0.9%
a_direct_floating = company_a["floating_spread"]
a_effective_with_swap = company_a["fixed"] - swap_rate_a_receives
a_savings = a_direct_floating - a_effective_with_swap
# B's net: pays SOFR + 1.0% to market, pays 5.4% to A, receives SOFR from A
# B's effective rate: SOFR + 1.0% + 5.4% - SOFR = 6.4%
# Without swap, B would pay 6.5%, so B saves 0.1%
b_direct_fixed = company_b["fixed"]
b_effective_with_swap = company_b["floating_spread"] + swap_rate_a_receives
b_savings = b_direct_fixed - b_effective_with_swapComparative Advantage in Interest Rate Swaps ======================================================= Borrowing Rates Company A Company B ------------------------------------------------------- Fixed Rate 5.0% 6.5% Floating Rate (SOFR +) 0.5% 1.0% ------------------------------------------------------- Difference in Fixed Markets 1.5% Difference in Floating Markets 0.5% Total Potential Gain 1.0% ------------------------------------------------------- With swap (A wants floating, B wants fixed): A's effective floating rate: SOFR - 0.4% A's savings vs direct floating: 0.9% per year B's effective fixed rate: 6.4% B's savings vs direct fixed: 0.1% per year
This example shows how swaps can create value. Company A has a comparative advantage in fixed-rate markets, while Company B's disadvantage is smaller in floating markets. By borrowing in their respective advantage markets and swapping, both companies end up with lower costs than if they had borrowed directly in their desired market.
Speculation on Interest Rates
Traders and investors also use swaps to express views on interest rate movements. A trader expecting rates to rise might enter a receive-fixed, pay-floating swap. If rates indeed rise, the floating payments they make increase, but the swap's market value also increases (since the fixed rate they receive becomes more valuable relative to new market rates).
Unlike buying or selling bonds, swaps require no upfront capital beyond margin requirements. This leverage makes them efficient instruments for taking directional positions on rates.