Flexible production has been the norm in Kolkata, which has an informal sector that employs more than 40% of the labour force.[1] One unorganised group, roadside hawkers, generated business worth ₹ 87.72 billion (US$ 2 billion) in 2005.[98] As of 2001[update], around 0.81% of the city's workforce was employed in the primary sector (agriculture, forestry, mining, etc.); 15.49% worked in the secondary sector (industrial and manufacturing); and 83.69% worked in the tertiary sector (service industries).[3]: 19 As of 2003[update], the majority of households in slums were engaged in occupations belonging to the informal sector; 36.5% were involved in servicing the urban middle class (as maids, drivers, etc.) and 22.2% were casual labourers.[4]: 11 About 34% of the available labour force in Kolkata slums were unemployed.[99]: 11 According to one estimate, almost a quarter of the population live on less than 27 rupees (equivalent to 45 US cents) per day.[100]