Mortgage borrowers are "locked in": forgoing moves to keep low rates. We show missing downsizers stay in larger homes, raising net demand. We design a spatial housing ladder model with long-term mortgages, generating a distribution of locked-in rates and causal mobility effects consistent with the data. A temporary rate hike causes lock-in, increasing house prices by 4.4% and rents by 1.4% relative to a counterfactual without lock-in, offsetting a third of the house-price decline caused by higher rates. A starter-home seller subsidy modestly increases mobility at a high cost per marginal move, suggesting demand-based policies are poorly targeted responses.

We study Danish fixed-rate mortgage contracts, which are identical to those in the United States except that borrowers may repurchase their mortgages at market value.

Using Danish administrative data, we show that households actively buy back debt when mortgage prices fall below par and that household mobility is largely insensitive when existing mortgage rates are below prevailing market rates --- unlike in the United States, where moving rates fall sharply as rates rise.

We develop an equilibrium model that explains these patterns and show that introducing a repurchase-at-market option into U.S. mortgages substantially reduces interest-rate-induced lock-in with limited effects on equilibrium mortgage rates.

This paper documents the extent of identity theft fraud and victimization costs. We find that between 2010 and 2022, over 26 million borrowers reported being victims. An average victim flagged two accounts on which they owed \$28,278. Victims, on average, take three years to detect fraud, which acts as the main friction driving long-run costs. Victims face reduced credit access, increased financial distress, and six-month delay in homeownership compared with non-victims. Delayed detection and credit demand shocks drive these costs. Low-income borrowers are more likely to become victims and incur higher costs, exacerbating credit access gaps over the income distribution.