Kenya is one of the world's leading exporters of black tea, featuring a mix of large-scale commercial estates and smallholders. While some larger estates have begun introducing mechanical tea-harvesting machines, manual hand-plucking remains highly valued for premium quality teas. It is estimated that the tea sector supports the livelihoods of more than 3 million Kenyans.
Briefly explain two factors that may affect the demand for labour on Kenyan tea estates.