Over 18.89 million bitcoins have been generated so far. The more there are, the more complex their production becomes. According to market specialists, roughly 20% of Bitcoins produced appear to be lost due to forgotten passwords and/or damaged hard drives.
The total amount that can be mined is technically limited to around 21 million Bitcoins. The uncovered currencies that are issued today by the central banks, on the other hand, can be produced in any quantity.
Thanks to the maximum supply, Bitcoin is resistant to inflation. When all Bitcoins are generated, miners will only earn transaction fees.