Abstract: The U.S. aggregate labour share has declined significantly since the mid-1980s. Traditional shift-share analyses attribute the decline to a common within-sector decrease in labour income relative to value-added, downplaying the contribution of sectoral reallocation. Using a refined decomposition method, I show that, by itself, reallocation toward high-labour-share sectors would have offset nearly half of the total decrease - an order of magnitude more than previously found. Instead, the co-movement of sectoral labour shares and reallocation drove the aggregate decline. Absent any reallocation between sectors, the labour share would have fallen only by half as much as it did.