Typically, postal votes must be mailed back before the scheduled election day. However, in some jurisdictions return methods may allow for dropping off the ballot in person via secure drop boxes or at voting centers. Postal votes may be processed by hand or scanned and counted electronically. The history of postal voting dates back to the 19th century, and modern-day procedures and availability vary by jurisdiction. Research, focused on the United States and using data from states where postal voting is widely available—California, Oregon and Washington—shows that the availability of postal voting tends to increase voter turnout.