In Vietnam, the regional differences between north and south are a topic of light banter that, if you dig too deep, can veer into taboo territory.

Northerners tend to take their food, including the staple pho soup, saltier than southerners, who like theirs sweeter. Residents of Ho Chi Minh City (also still widely known as Saigon) in the south will tell you they are quicker to smile than Hanoians in the north, who they see as diligent but austere — po-faced even. Hanoians see Saigoneers as more entrepreneurial and cosmopolitan but too spendthrift, people who both work and play hard.

The north-south rivalry is likely to come into focus this month, as communist lawmakers discuss a draft securities law that would merge the two cities’ equity markets into a single Vietnam Stock Exchange. One of the topics to be addressed is whether the new market will be in the capital of Hanoi (population 8m), or Ho Chi Minh City, the business hub of 9-10m.