Official figures have shown.

The difference in average wages between men and women in full-time employment in the UK has narrowed slightly this year, official figures have shown.
Males in full-time employment earned an average of £12.97 an hour before tax compared with £11.39 for women, said the Office for National Statistics.
This means women earn on average 12.2% less than men, although this is less than the gap of 12.6% recorded in 2008.
The ONS data came from a survey of 177,000 people conducted in April.
The figures do not include overtime, as men tend to do more of this, the ONS said.
It found that the gender pay gap continued to differ widely between different kinds of work.
The gap was narrowest for those in professional jobs, such as in banking, where men earn just 3.8% more.
The difference in pay was the largest in the skilled trades category - a wide sector that includes everything from plumbers to florists - where the gap reached 26.2%.