Two main types of research have been carried out extensively in this field. The first is establishing correlations between superior business performance as measured against a range of indicators and the presence of HR practices in thousands of organizations. Major examples of this kind of research are the studies carried out by Huselid (1995) in the USA and by Guest and his colleagues (2003) in the UK.
The second involves seeking to establish through interview in successful case study organizations what factors have contributed to their growth, profitability, quality of service, etc.