What Would Have Happened
The third, or 'past', conditional is used to imagine past outcomes different than what actually took place. This conditional is used to express what would have been different if a person had done something differently.
'If' clause - past perfect + , + result clause - would + have + verb (conditional perfect tense)
If they had known about the project before, this project wouldn't be listed on short notice.
If the homebuilder had predicted the speculative bubble they would have laid off more employees.
If I had opened the account when it was available, would I have been offered overdraft protection?
Payments on the student loan's deferred interest would not have been a problem if the economy had been better.
Examples of Past Unreal Outcomes
Do not use a comma, when placing the result clause first.
He would have invested in the futures market if he'd had more confidence in the economy.
The capital allowance would have been granted if the merger had been approved by regulators.