Without unions (or minimum-wage laws), the price of labour reflects supply and demand. Skills in shortage have higher wages; unskilled labour drops to starvation wages - or below, provided there are replacement people.<p>In good times, with labour in demand, wages are higher, up to the point where the demand is met. Wages can go no higher. If there are enough people, these wages might be quite low. The remaining surplus is captured by capital.<p>In bad times, when demand for labour is low, wages may drop arbitrarily low.<p>Another solution to starvation-wages or below is social security or, more radical, universal income. It acts like an employer competing for labour, providing a minimum-wage threshold, through market forces. If capital doesn't offer sufficient wages, labour chooses the safety net.<p>However, this ignores the non-wage benefits of employment: people <i>like</i> to work, to be important/needed/useful, to be part of something, social contact, etc not to mention practice and acquisition of skills.<p>Finally, to be fair to pg, unions also represent a freezing of a particular way of doing business. Like back-compatibility or a requirement to use a particular technology, it restricts the way work can be organized. It prevents work from being "re-factored" - even if there exists another arrangement that would be just as good or even better for workers.
Inflexibility eventually causes inefficiency.<p>[ BTW I think there are three levels of systems that we can optimise for "efficiency": technical systems are efficient at their task; a business as a system is efficient at making money; a society as a system is efficient being something people want to be part of - that is, serving their needs. ]