One of the unfortunate facts of political and social life in Belfast is that the two communities are in many ways strangers to each other in how they live, worship and are educated.
The revelation that in the area of housing separation is almost complete has ominous implications for those who hope the peace process will bring reconciliation in the foreseeable future.
Segregation in Belfast housing is long standing. It began when large numbers of Catholics moved into the almost exclusively Protestant city in Victorian times and clustered in districts such as Falls and Ardoyne. A degree of segregation is often assumed to be natural, and employment in Northern Ireland has become less segregated than it was. But well over 90 per cent of children continue to be educated in separate schools.
Post-Troubles Northern Ireland is now facing the unwelcome fact that what has been called apartheid is now virtually complete for the working class.
Few safe refuges exist for mixed marriages and those who dislike segregation.
The ingrained divisions are starkly obvious in parts of north and west Belfast where high barriers known as peace lines divide - some say deface - the urban landscape.
In other areas roads and commercial and industrial zones serve the purpose of keeping the two sides apart.
More than two dozen peace lines have become permanent features, some of them tastefully draped with ivy and shrubs to soften their grim purpose, but the figures show that invisible yet potent boundary lines exist in most other parts of the city as well.
The irony of the peace process is that the IRA and loyalist ceasefires, which were declared exactly 10 years ago, have been followed by a decrease in deaths but no reduction in community tensions.
In fact, several more peace lines have been erected since then.
The continuation of disturbances in cockpit areas such as north Belfast, both in terms of occasional street riots and of lower-level intimidation, has continued to force the two communities apart.
"It's called the ratchet effect," said one housing specialist. "Very often when there are local disturbances people move out. They may go only in very small numbers - but they never ever go back."
Over two centuries Belfast has seen a cycle of separation, with measures of integration suddenly reversed by new outbreaks of rioting.
While many assumed the ceasefires would result in a drawing together of the communities, they have in fact been followed by near-total segregation. The authorities therefore face a daunting task in aiming to reverse the so far inexorable tide of polarisation and working towards a more tolerant and inclusive society.
Evidently, not all of those who live in segregated areas oppose integration, though the safety factor alone has been enough to convince many that integrated housing brings physical dangers and is best avoided.
This mindset means that segregation is destined to be the norm for many years to come. It is both a product of community division and a factor which makes those divisions worse.Reuse content