  In research policy, effective measures that lead to improvements in the
generation of knowledge must be based on reliable methods of research
assessment, but for many countries and institutions this is not the case.
Publication and citation analyses can be used to estimate the part played by
countries and institutions in the global progress of knowledge, but a concrete
method of estimation is far from evident. The challenge arises because
publications that report real progress of knowledge form an extremely low
proportion of all publications; in most countries and institutions such
contributions appear less than once per year. One way to overcome this
difficulty is to calculate probabilities instead of counting the rare events on
which scientific progress is based. This study reviews and summarizes several
recent publications, and adds new results that demonstrate that the citation
distribution of normal publications allows the probability of the infrequent
events that support the progress of knowledge to be calculated.
