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A fundamental refashioning of the labor market has been underway for two decades. Jobs that require middle-range skills have been declining, while those involving skills at both the lower and higher end of the spectrum have been growing. This effectively suppresses wages for many: People in lower-paid, lower-skill jobs — retail workers, janitors and home health aides — have little bargaining power to demand higher wages. Middle-skilled workers — including clerks, call center operators and factory workers — are being replaced by computers, robots and lesser-paid hands in low-wage countries. Higher-skilled workers are capturing an outsized share of pay.