Firms choose how to produce the goods and services they sell. In many cases, firms face a trade-off between using more workers or using more machines. For example,

It depends upon the economical situation. For example if we talk about USA, the labour here costs more than China, whereas in USA machines are less costly than China which means USA can only benefit globally if its products have lower cost from China (China is the biggest competitor of USA) by using fewer labour and relying more on machines.