World Bank

…the most important groups are manual laborers—whose fingerprints tend to wear off from excessive use of their hands—and children, whose fingerprints are not fully developed or undergo changes with development; as well as the disabled or amputees. These challenging cases require adopting exception-handling protocols (which may be relevant for 1 to 2 percent of the population) in order to ensure total inclusion. Exception handling for biometric capture may include the use of: newer fingerprint scanners based on thin film imaging devices (e.g., Light-Emitting Sensors) instead of traditional optical sensors.

- World Bank