1950 Population: 3,620,962
2010 Population: 2,695,598
1950-2010 Change: -25.6%
2000-2010 Change: -6.9%
2010-2012 Change: +0.7% (estimate)
1950 Population: 2,071,605
2010 Population: 1,526,006
1950-2010 Change: -26.3%
2000-2010 Change: +0.6%
2010-2012 Change: +1.4% (estimate)
1950 Population: 949,708
2010 Population: 620,961
1950-2010 Change: -34.6%
2000-2010 Change: -4.6%
2010-2012 Change: +0.1% (estimate)
1950 Population: 503,998
2010 Population: 296,945
1950-2010 Change: -41.1%
2000-2010 Change: -10.4%
2010-2012 Change: -0.1% (estimate)
1950 Population: 570,445
2010 Population: 343,829
1950-2010 Change: -39.7% (-45.2% since 1960 peak)
2000-2010 Change: -29.1%
2010-2012 Change: +7.4% (estimate)
1951 Population: 1,247,627 (within the 2011 city limits)
2011 Population: 1,649,519
1951-2011 Change: +32.2%
The American cities appear to have reached the point where they are no longer losing population as a whole.
Philadelphia saw moderate population gains in Center City, but the surrounding neighbourhoods experienced significant population losses, especially in the inner north side. These losses were still not quite as bad as in the more hard hit cities. Going further from Center City, losses get smaller and smaller, until one reaches the outermost neighbourhoods which saw population gains. The outer Northeast was evidently built mostly post-1950.
Baltimore experienced a bit worse population loss in the core than Philadelphia, while outer neighbourhoods saw little population change. The inner 18.7 square miles of Baltimore went from holding 54% to 33% of the city's population.
Inner 18.7 sq mi
Outer 62.2 sq mi
In 1951 the areas that lost population held 787,690 people, and lost 326,513 (-42.9%). This compares to a 1951 population of 1,247,627 for the area within the 2011 city limits (highlighted areas on the map), so a big chunk of the city. In cases like the neighbourhood east of Downtown (69% loss), there was some population due to urban renewal and expansion of the CBD's commercial and institutional uses. However, in the neighbourhoods that lost 32-47% of their population, loss of residential uses was negligible, and in some cases, there was intensification through new construction and brownfield redevelopment (perhaps even a bit of greenfield growth).
Household size decreases* in Montreal probably led to greater population decreases than in the average American city, but it nonetheless helps provide some context for discussions about the effect of household size changes.
Some of these Montreal neighbourhoods had even greater populations in 1941. Whether they lost population prior to that too is unclear. 1931 population data by ward is available, however, no map of the wards is provided, and the names given to wards are no longer in use for present day neighbourhoods, so it's difficult to know what areas they refer to (does anyone know?). It's certainly possible that they would have lost population prior to WWII though, neighbourhoods of New York, Paris and London all lost population prior to WWII due to decrowding. The industrial and commercial part of Montreal was already expanding into the formerly residential old "faubourgs" at that time (now part of downtown). Elsewhere it's less clear, Montreal was not as "mature" as Paris in the early 20th century, neighbourhood densities were lower, and it's possible they intensified enough to counter the effect of household size decreases.
*In this blog, household size decreases will usually refer to household decreases but also other forms of decrowding such as combining smaller units into larger ones, as long as the building density doesn't decrease.