Morrison argues it's his military-style operation, headed by a three-star general, that is responsible for the late-year drop-off in numbers.
Others, especially Labor, credit the so-called Papua New Guinea solution introduced by former Prime Minister Kevin Rudd before the election.
A week-by-week analysis of arrivals between July and November lends weight to that view.
It reveals a downward trend, from an initial peak of a dozen boats a week to three complete weeks of no boats during October and early November.
As far as Morrison is concerned, the secrecy surrounding Sovereign Borders is a deliberate strategy to stop information getting to people smugglers and their potential clients. "We're not a shipping news service," he says when asked for specific details of interceptions.
The outlook though is not as rosy as the Government likes to make out.
The fallout from a spying scandal has ended, for the time being, the co-operation of Jakarta. Indonesian national police are adopting a hands-off approach to people smugglers. The Prime Minister hopes good relations will be restored by the time the monsoon season - a no-go period for boat travel - ends in February.
The Abbott Government also faces budgetary pressures with the cost of running offshore detention centres blowing out by A$1.2 billion ($1.3 billion). Offshore processing of asylum seekers will cost A$2 billion over the next four years.
- AAP