When it comes to maximum benefit pensions, like exist in most developed democracies, you can pick two of the three when your population is not growing fast enough to cover future benefits:
- Stable currency
- High benefits
- Low taxes (yes, really)
If you choose to keep benefits high and not increase taxes, you will need to print money to cover benefits at a sustained level level, which will likely cause inflation.
Tax rates need to increase if you keep benefits high and keep a stable currency.
Benefits will need to be reduced to keep taxes low and keep a stable currency.
Or you could just use superannuation like Australia and Singapore.