Despite making a massive contribution to China's economy, delivery workers still endure long hours, low wages and poor job security. Hou Liqiang reports.

Wrapped warmly in leather leg chaps, gloves and a Russian hat with ear flaps, Yang Lei appeared well-equipped to survive the winter as a delivery courier in Beijing.

He works seven days a week, but his monthly salary of about 5,000 yuan ($723) - the average for delivery drivers - is chickenfeed given the hours he works for his employer, Tiantian Express, and the contribution couriers make to the national economy.