Expansion without diversification: Growth and rising concentration by source country in Malaysia’s registered foreign construction workforce, 2020–2023

Malaysia’s total fertility rate has been below the replacement level since 2013; its population is aging​, and non-citizens made up 8.9% of residents in 2023. Construction is one of the sectors that is most dependent on migrant workers. This study examines whether the growth in the foreign construction workforce registered with the Construction Industry Development Board (CIDB) broadened or narrowed its distribution across source countries. Using unpublished country-by-year counts for 11 origin categories supplied by the CIDB, we calculated the annual and compound growth rates, country shares, concentration ratios (CR1 to CR4), Herfindahl–Hirschman index (HHI), entropy-based diversity measures, and a proportional-growth counterfactual. The number of registered workers fell by 17.6% in 2021 and then rose to 385,503 in 2023, which is 2.25 times the 2020 level of 171,412. Bangladesh accounted for 80.7% of the total net increase. The HHI rose from 3,950.7 to 5,151.8, and the effective number of source countries fell from 2.53 to 1.94. Bangladesh’s share rose by 13.4 percentage points, and Indonesia’s fell by 12.1 points; thus, the combined share of the two largest origins (CR2) moved only from 82.8% to 84.2%. The near-constant CR2 concealed a large shift in shares within the leading pair, which arose from differential growth rather than a decline in Indonesian registrations. This pattern holds when the 2021 trough is used as the base year and when the residual category is excluded, and growth is not reliably associated with initial size. In conclusion, the registered workforce expanded without any diversification. Registry counts cannot identify the recruitment, policy, or sending-country processes behind this pattern, and concentration measures do not indicate anticompetitive conduct.