The inclusion of Business Angels in the range of ‘informal’ (as opposed to ‘institutional’) investors provides us an indication that there are potential difficulties in measuring the size of the Business Angel community. Mason and Harrison identify two main problems, identification and definition. Regarding the former, in his seminal work on Business Angels, William Wetzel (1983) notes that the total population of Business Angels is unknown and probably unknowable on account of their invisibility, desire for anonymity, and the undocumented nature of their investing. Most studies are based on samples of convenience, such as angels who are members of Business.
