Abstract
Texts, encyclopedia entries and other sources of information on ethnic populations invariably include data on their numbers. This seemingly straightforward fact, though, includes numerous pitfalls and questions which are difficult to answer and solve.
The purpose of this paper is to draw attention to some of these facts. In the first place, phenomena of ethnicity and language are two main starting points of official censuses and other ethnicity oriented statistics are being looked into and analysed.
The author points out problems of the received data, which are often of purely subjective character, and stresses the need to analyse and interpret them in greater detail and more deeply. In addition, the paper includes brief comments on other phenomena affecting results of ethnicity and language statistics: the role of territory appurtenance, exogamy partnership, dual/multiple identity, populations without ethnic selfidentification or the factor of ethnic origin.