MORE sick days are taken in January than in any other month, as employees shun the chilly weather for a day under the duvet. Yet some firms are finding that their workers are not coming back at all after the Christmas break. A week back in the home country sometimes persuades migrant workers from the European Union to stay there. As well as the British weather, they now face a weak pound—and, of course, the looming prospect of Brexit.

Since the vote in 2016 to leave the EU there has been a sharp rise in the number of European migrants leaving Britain. In the year to June 2017 a total of 123,000 packed their bags, 28,000 more than during the previous year. Overall, net migration of EU citizens fell by 43%; among those from the “A8” countries of central and eastern Europe, it fell by 81%.

The drop threatens to compound the difficulty of recruiting workers in what is already a tight labour market. Unemployment, at 4.3%, is at its lowest since 1975. Firms in some industries are struggling to fill vacancies. Among skilled trades, chefs are particularly in demand. A report commissioned by the construction industry in 2016 warned that within a decade the pool of labourers could shrink by 20-25%.

Some argue that having fewer workers would do Britain good. The abundance of foreign labour in recent years has helped to keep a lid on wages in some low-paid jobs. With fewer migrant workers, firms might be forced to train lumpen locals and invest more in technology, thus improving Britain’s poor productivity. That argument was given a boost this month by figures showing that productivity grew by nearly 1% in the third quarter of last year, the sharpest rise since 2011 (albeit following a bad first half of the year).

Yet the signs are that firms are being slow to respond to the drying up of the labour pool. Their first course of action might be to pay higher wages, in order to recruit more local workers and retain EU employees. Some employers have done this. Real annual wages in agriculture, which is particularly vulnerable to any decline in migrant workers, increased by over 3% in the three months to October, more than any other industry. Other migrant-heavy businesses, however, have done just the opposite: wages in food manufacturing fell by 1% and those in construction by 0.2% during the same period.

Improving conditions would be another way to fill vacancies. Andrew Green, head of the Craft Guild of Chefs, says that the culture of bullying in kitchens pushes new recruits out of the profession just as much as the low wages. He remembers the roasting trays and pots flying in his direction decades ago, and acknowledges that little has changed. Some restaurants are tackling the 70-hour weeks that chefs often have to work. Several Michelin-starred restaurants, including Le Gavroche in London and Sat Bains in Nottingham, have reduced their opening hours to retain staff. Similarly, the Road Haulage Association is to launch a campaign to advertise better working conditions for drivers, of whom there is a national shortage.

If firms cannot hang on to people, they may replace them with machines. Robots tend not to make good chefs, even if they are less prone to tantrums. But in other industries, such as food manufacturing and agriculture, there is considerable scope for further automation. The Resolution Foundation, a think-tank, has estimated that 10-35% of today’s jobs could be automated by the early 2030s. Sensors are already so highly developed that at a factory run by Premier Foods, near Sheffield, a machine can pick up brittle poppadums from a line and bag them, removing the need to employ five pairs of human hands.

Yet Britain is lagging behind in its use of robots (see chart). Martin Howarth, director of the National Centre of Excellence for Food Engineering at Sheffield Hallam University, warns that automation in food manufacturing is low, behind countries such as Germany and Japan. According to the Institute for Public Policy Research, a think-tank, capital investment in Britain’s low-wage industries, as a percentage of their output, is about 14%, compared with 15% in France and over 20% in Germany.