So, how much would a united Ireland really cost?
Smart Money: Who would pay for a united Ireland economy and might other gains help pay the bill?
Reunification is ultimately a political issue, of course, but economics is a big part of it.
Depending on which report you believe, uniting the two Irish economies – North and South – could either lead to a dive in living standards in the Republic, or a big economic boost for the entire island.
As the issue hits the headlines again in the context of Brexit, how do we judge these various arguments – and what are the key factors at play?