Unit 2: UK trade deficit worsens

Several sources showing the worsening trade deficit

http://news.bbc.co.uk/1/hi/business/8558908.stm video
http://news.bbc.co.uk/1/hi/business/8557200.stm article
http://www.anforme.co.uk/blog/?p=1233 article

a) Explain how the trade deficit is calculated
b) Explain how a weaker pound should improve the trade deficit
c) Explain why this hasn't happened
d) To what extent should the UK economy worry about this trade deficit?