Amid the materials shortages, price hikes and other craziness of the housing market last year, something remarkable happened. US builders completed more apartments in large multi-unit buildings than ever before. …This news may come as something of a surprise amid a pandemic that emptied downtown office buildings and brought real estate bidding wars to outer suburbs and mountain resorts. Big apartment buildings don’t really seem to match the moment. …The disappearance of this “missing middle” between single-family houses and larger multifamily structures has been much lamented. …According to Characteristics of New Housing data, 77% of the multifamily units completed in 2021 were in wood-framed buildings. While “mass timber” buildings of up to 18 stories are now allowed, “stick” framing is the standard in US wood-framed apartment construction. …But why the shift from small apartment buildings to big? I don’t think consumer demand really explains it.