Long-Term Debt and Short-Term Rates: Fixed-Rate Mortgages and Monetary Transmission

Mon, 01 Jan 0001 00:00:00 +0000

This paper uses instrumental-variable local projections (IV-LP) on an unbalanced panel of up to 35 countries over approximately two decades to establish two interconnected findings about fixed-rate mortgages (FRMs) and monetary policy. First, monetary policy affects mortgage type selection: a 100 basis point tightening increases the share of adjustable-rate mortgages (ARMs) in new originations by approximately 10 percentage points after one year, while easing generates the reverse shift toward FRMs. The mechanism is budget constraints: ARM rates move nearly one-for-one with policy rates while FRM rates respond by only about 0.5 percentage points per 100 bps, so after tightening the FRM-ARM spread narrows but both products become more expensive — households facing tighter budgets select the cheaper ARM option, irrespective of spread comparisons. Second, the prevailing stock composition of outstanding ARMs determines how strongly monetary policy transmits to real activity: for every additional percentage point of household debt held as ARMs, the same 100 bps policy change produces approximately 0.05 percentage points more impact on real private consumption at six quarters ahead, controlling for the level of household debt-to-GDP. A back-of-the-envelope calculation implies that the same 100 bps change induces a consumption response approximately 5 percentage points stronger in an economy with 100 percent ARMs versus one with only FRMs. These two findings jointly imply that FRMs create both path-dependency (past easing cycles populate the stock with FRMs, weakening future transmission) and state-dependency (current FRM prevalence determines how much a given rate change moves consumption and GDP) in monetary policy.

Summary of a forthcoming paper, AI-assisted and human-reviewed. See the linked original for the authoritative claims and full conditions.

In depth

The paper draws on two data sources: flow data covering new mortgage originations in 27 countries and stock data on the outstanding mortgage composition in 35 countries, spanning approximately two decades of quarterly observations. A mortgage is classified as fixed-rate (FRM) if the contractual interest rate is fixed for 12 months or more from origination; below that threshold it is classified as adjustable-rate (ARM). This definition aligns with ECB and Eurostat conventions and is consistent across the panel, though note that some “fixed-rate” mortgages in the sample include hybrid products with initial fixed periods that eventually reprice. The FRM share in new flows (used in the path-dependency analysis, equation 2) captures how the composition of new originations responds to monetary policy. The FRM share in outstanding stock — expressed as a proportion of household debt-to-GDP (ARMdebt) — is the state variable in the state-dependency analysis (equation 3). Countries’ time-series for both measures display the expected patterns: in the long period of ultra-low rates following the GFC, the FRM share in stock increased substantially across the sample.

Q2. How are monetary policy shocks identified and why are information effects excluded?

Monetary policy shocks are constructed from Bloomberg high-frequency financial market surprises around central bank announcement windows, then orthogonalized with respect to the central bank’s private information component using the Bauer and Swanson (2023) procedure. The Bauer-Swanson orthogonalization removes the portion of policy surprises that is correlated with the central bank’s assessment of the economic outlook — the “Fed information effect” identified by Nakamura and Steinsson (2018). Without this purification, a policy surprise that partly reflects the central bank’s private negative news about growth would confound the identification: the estimated consumption response would reflect both the direct policy-rate effect and the information revelation, making it impossible to isolate the transmission mechanism through mortgage types. The first-stage Kleibergen-Paap Wald F statistics are 34 or above for the path-dependency regression (equation 2) and 12.9 or above for the state-dependency interaction regression (equation 3), satisfying standard relevance thresholds.

Q3. What is the path-dependency mechanism and what does Figure 3 show?

Figure 3 plots impulse responses of FRM rates, ARM rates, 10-year and 1-year government bond yields, the FRM-ARM spread, and the ARM share in new flows to a one percentage point policy rate change instrumented with the Bauer-Swanson-cleaned shocks. FRM rates respond by approximately 0.5 percentage points per 100 bps of policy change, similar to the response of 10-year government bond yields, with full reversion after about 4–6 quarters. ARM rates respond approximately one-for-one, similar to 1-year yields, also reverting after 4–6 quarters. Since ARM rates respond more than FRM rates, the FRM-ARM spread narrows by about 0.5 percentage points after a 100 bps tightening — making ARMs relatively cheaper compared to FRMs. Despite this narrowing of the spread (which should theoretically discourage ARM selection), the paper finds that ARM share in new flows increases significantly: a 100 bps tightening raises the ARM share by approximately 10 percentage points after one year, a large effect corresponding to about two thirds of a within-country standard deviation. The paper attributes this to budget constraints: even though the FRM-ARM spread narrows, both products become more expensive in absolute terms, and cash-constrained borrowers choose the cheaper option (ARM) to minimize initial monthly payments, rather than comparing relative spreads. The converse holds during loosening: as borrowing costs decline and budget constraints ease, borrowers show a revealed preference for the interest rate risk protection of FRMs, consistent with a general preference for payment certainty when affordability is not binding.

Q4. How does the mortgage stock composition affect monetary policy transmission (state-dependency)?

The state-dependency analysis (equation 3, Figure 4) regresses macroeconomic outcomes on the interaction of a policy rate change and the ex-ante ARM debt share (ARMs as a proportion of household debt-to-GDP), using country and quarter fixed effects with Driscoll-Kraay standard errors and IV identification. The left column of Figure 4 shows that the marginal effect of a 100 bps policy change on real private consumption increases by approximately 0.05 percentage points for each additional percentage point of ARMs in outstanding stock, a differential that becomes noticeable after about six quarters. The differential response for durables consumption appears earlier (around two quarters), while the real GDP differential is roughly half the consumption differential (about 0.02 percent per percentage point of ARM debt). The right column of Figure 4 separates the state variable into the pure ARM share and household debt-to-GDP by including both interaction terms in a horse-race specification. The paper finds that the ARM share (not the debt level) drives the transmission differences for real GDP and both measures of consumption, consistent with a cash-flow channel interpretation: it is interest rate resets on existing ARM contracts that affect disposable income flows and spending, not the debt level per se. Household debt-to-GDP is relevant for durables consumption, potentially reflecting wealth and collateral effects on credit-intensive spending categories. The 100 percent ARM versus 0 percent ARM back-of-the-envelope calculation implies a 5 percentage point consumption difference per 100 bps, corresponding exactly to one standard deviation in cumulative real private consumption changes at 6 quarters in this sample.

Q5. Why is the shift toward ARMs after tightening paradoxical given the standard relative pricing model, and what channels can explain it?

The standard framework predicts that borrowers choose FRMs when the FRM-ARM spread is low (ARMs relatively less attractive) and ARMs when the spread is high; a tightening that narrows the spread should therefore shift borrowers toward FRMs, not ARMs. The paper finds the opposite and offers two channels. First, a budget constraint channel: after tightening, both FRM and ARM rates rise in absolute terms, but ARMs remain cheaper at origination because they carry lower initial payments; liquidity-constrained borrowers facing higher total borrowing costs choose the cheaper option regardless of the spread direction, consistent with evidence in Andersen et al. (2023) that ARM adoption is more prevalent among liquidity-constrained borrowers. Second, a cost-minimization channel with short-run focus: some borrowers choose the product that minimizes current-period mortgage payments, not lifetime payments; after tightening, ARMs minimize the monthly payment even though they expose borrowers to future rate risk. The paper notes that the converse — FRM adoption after loosening despite rising FRM-ARM spreads — cannot be explained by short-run cost minimization and suggests a preference for rate certainty when affordability is non-binding.

Q6. Is the state-dependency effect asymmetric between tightening and loosening cycles?

The paper tests an asymmetric specification and finds that FRMs are a greater impairment to monetary transmission during tightening relative to loosening cycles, especially when free prepayment options are available. During tightening, a high FRM share means few borrowers face rate resets on their existing debt, so the cash-flow channel is weak; simultaneously, prepayment refinancing into new mortgages is unattractive (locking in a higher rate) so the existing FRM stock remains insulated. During loosening, a high FRM share means borrowers can refinance into lower FRM rates or into ARMs at lower cost, partially restoring the transmission channel. This asymmetry is consistent with findings in Berger, Milbradt, Tourre, and Vavra (2021) on mortgage prepayment and path-dependent monetary policy effects in the US, and suggests that the FRM-induced weakening of transmission is particularly binding precisely during contractionary cycles when central banks most need the transmission mechanism to be operative.

Q7. What are the implications for central bank transmission assessment and policy?

The two findings together imply that monetary policy transmission capacity is endogenous to the history of the policy cycle. A prolonged loosening phase (such as the post-GFC decade of ultra-low rates) shifts new originations toward FRMs, which accumulate in the outstanding stock; the resulting high FRM share means that subsequent tightening operates through a weakened transmission channel. The central bank’s policy instrument affects the transmission mechanism’s own strength. This endogeneity has at least two practical implications. First, central banks that have conditioned borrowers into expecting prolonged low rates may face amplified instrument-calibration uncertainty: the same 100 bps tightening has systematically weaker real effects in economies where prior easing locked in high FRM shares, requiring larger policy moves to achieve the same macroeconomic stabilization. Second, cross-country heterogeneity in the FRM-ARM mix — itself partly endogenous to the history of monetary policy — explains a significant portion of the observed heterogeneity in monetary policy transmission strength across countries, complementing structural explanations based on financial market depth, indebtedness levels, and household balance sheet composition.

Key concepts

fixed-rate mortgage (FRM): a mortgage with a contractual interest rate fixed for 12 months or more; holders are contractually insulated from subsequent policy rate changes, reducing the pass-through of monetary policy to household debt service costs through the cash-flow channel; in the paper’s framework, FRM prevalence is both a consequence of past policy (path-dependency) and a determinant of current transmission strength (state-dependency).

adjustable-rate mortgage (ARM): a mortgage where the interest rate resets with market rates (at intervals shorter than 12 months for the paper’s classification); holders feel policy rate changes immediately in their monthly payments, amplifying the cash-flow channel; the paper finds ARM share in new flows rises after monetary tightening due to budget constraint effects.

path-dependency: the property that the current effectiveness of monetary policy depends on the accumulated history of prior policy rate changes, through their effect on the outstanding mortgage stock composition; specifically, prolonged easing cycles generate high FRM shares that reduce future transmission potency.

state-dependency: the variation in monetary policy transmission strength with the prevailing share of ARMs in outstanding mortgage debt; the same policy rate change produces a consumption response approximately 5 percentage points larger in a 100 percent ARM economy than in a 100 percent FRM economy (per 100 bps), controlling for debt-to-GDP.

cash-flow channel of monetary policy: the mechanism by which changes in policy rates affect households’ disposable income through resets in the interest payments on their existing variable-rate debt; the dominant channel in the paper’s state-dependency results — ARM share (not debt level) drives transmission differences for consumption and GDP, consistent with income flow effects on spending propensity.

IV local projections (IV-LP): the estimation framework combining Jordà (2005) local projections — a flexible, model-free method for estimating impulse responses at multiple horizons — with instrumental variable identification using Bauer-Swanson-cleaned monetary policy shocks; used for both the path-dependency regressions (equation 2, ARM flow response) and the state-dependency regressions (equation 3, interaction with ARM stock).

Bauer-Swanson (2023) information effect correction: the procedure for removing the component of high-frequency monetary policy surprises that is correlated with the central bank’s private information about economic conditions; applied here to prevent the estimated transmission effects from conflating pure rate changes with information revelation about the macroeconomic outlook.

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