Contends that investors and valuers are relying unduly on retail market data of limited usefulness and low predictive power, affecting their ability to assess rental growth rates for individual retail properties. Looks at the special relationship of retail property to location choices, the unusual interaction between supply and demand in the town-centre retail sector as they affect rent levels and the retail location issue from the investors' perspective. Argues that the links between rental growth, town size and wealth are, unsurprisingly, rather weak, given the fragility of the data upon which they are based. Reviews new approaches to collating and monitoring effective retail demand levels. Asks how the investor or valuer is to choose rental growth rates and whether their rental growth assessments are efficient. Figures cover shop rental growth and centre size, shop rental growth and wealth, sales growth and the annualised shop rental growth range 1999-02