The actual incidence outside of a hospital setting is impossible to determine. In a large study in Israel, spontaneous pneumothoraces occurred in 723 (60.3%) of 1199 cases; of these, 218 were primary and 505 were secondary. Traumatic pneumothorax occurred in 403 (33.6%) patients, 73 (18.1%) of whom had iatrogenic pneumothorax.
In a recent study, 12% of patients with asymptomatic chest stab wounds had a delayed pneumothorax or hemothorax.