Historically, many key theories of urbanization and urban development have emphasized the city’s role as a central marketplace for goods and services, noting the ability of cities to attract customers from a wide hinterland. As has been emphasized in previous chapters, sex is one commodity that is bought and sold in cities – one that is often highly valued – yet its importance in supporting the growth and expansion of cities is seldom acknowledged in this literature. In part, the reticence among urban theorists to acknowledge that sex commerce makes an important contribution to urban economies is related to the fact that sex markets often exist outside, or alongside, the formal economy (Sanders 2009b). As was described in Chapter Two, the sale of sex often occurs out of sight of the state and law, behind closed doors and ‘in the shadows’. As such, the contribution that sex businesses make to the urban economy is often hard to gauge.