This paper examines deposit stickiness using account-level data from over 10 million retail accounts across 152 U.S. credit unions. We find significant skewness in deposit distributions, with 10% of depositors controlling 70% of total deposits. Low-balance depositors are sensitive to exogenous interest rate changes, but high-balance depositors are not. High-balance depositors are also relatively insensitive to discontinuous rate jumps at specific balance thresholds and are more likely to experience large, sudden withdrawals. Taken together, our evidence suggests that aggregate deposit stickiness is driven by relatively few high-balance accounts that are used as medium-run liquidity stores rather than for long-term savings.