Graeme Ramsey, chief executive of the Problem Gambling Foundation, said New Zealand effectively copied Australia by letting in poker machines in the late 1980s because thousands of Kiwis were already using them on visits to New South Wales league clubs.
"Even though we have gone down, we are still high in world terms," he said. "There is no history of gambling before Europeans arrived in New Zealand, but in our early history we had huge amounts of gambling.
The first race meeting was five years before the Treaty of Waitangi. We were described as a 'rugby, racing and beer' society, so I think gambling was quite ingrained in our culture.
"Then in the 1980s it absolutely exploded with the introduction of pokie machines from Australia, and that really was a reflection of what was happening in Australia."
Internal Affairs Department statistics show that gambling losses increased from $614 million in 1994 to just over $2 billion in 2004, but have levelled off since a new Gambling Act, which took effect in 2004 and allowed local councils to impose "sinking lids" on pokie numbers.
H2's statistics imply total losses of $2.3 billion last year, slightly higher than the last Internal Affairs figure of $2.1 billion for 2014, reflecting H2's estimate of unmeasured Kiwi gambling on overseas betting sites.
The world rankings are also affected by shifting exchange rates. The US has risen up the ranks partly because of a 20 per cent rise in the US dollar against the euro in the two years since the Economist published its league table.