The four sentences (labelled $1,2,3$ and 4 ) below, when properly sequenced would yield a coherent paragraph. Decide on the proper sequencing of the order of the sentences and key in the sequence of the four numbers as your answer:

1. Businesses find automation, such as robotic employees, a big asset in terms of productivity and efficiency.

2. But in recent years, robotics has had increasing impacts on unemployment, not just of manual labour, as computers are rapidly handling some white-collar and service-sector work.

3. For years politicians have promised workers that they would bring back their jobs by clamping down on trade, offshoring and immigration.

4. Economists, based on their research, say that the bigger threat to jobs now is not globalisation but automation.