Hi, I wonder what is here "a component of bargaining power" - "strike action" or "mobilisation on the street"? Thank you.
"If membership density or financial resources are modest, mobilisation on the streets may be easier than sustained strike action, which is a component of bargaining power, even if not its only source." (Trade Unions in Western Europe: Hard Times, Hard Choices)
The 'which' refers back to the nearest antecedent – 'sustained strike action'.