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Abstract
The sustained decline of the labor share challenges the classic
Kaldor facts. This paper proposes a “weighting effect” mechanism: because large
firms systematically adopt more capital-intensive technologies, a shift of
economic activity toward large firms mechanically depresses the macro labor
share, even under perfect competition. We test this mechanism by exploiting
minimum wage hikes in China as an exogenous shock that forces small
labor-intensive firms to exit. Using the Chinese Annual Survey of Industrial
Firms (1998–2007) and a Bartik instrument based on pre-sample small-firm shares
interacted with provincial minimum wage growth, we find that a
one-standard-deviation shock reduces the market-level labor share by
approximately 0.11 percentage points (3.5% of the mean). The effect is robust
to controlling for market concentration, alternative measures, and a battery of
placebo tests including randomization inference. Direct mechanism tests confirm
that the shock raises exit rates, reduces the number and share of small firms,
and reallocates output toward large, capital-intensive firms. Supplementary IV
estimates confirm that a more equal firm size distribution raises the labor
share. The findings identify a complete causal chain from labor market institutions
to macro distribution through the firm size structure, offering a
“technology-structure” channel that is independent of market power.
JEL classification numbers: J31, L11.
Keywords: Labor share, Firm size distribution, Minimum wage, Weighting
effect, Bartik instrument.