We would like to emphasise that the number of prizes in each category is not limited. Due to that changes of some scores, following, for example, a discussion between the heads of the delegations and the markers, resulting in a "shift" of some participants from, for example, the group of second prize winners to the group of first prize winners, the category of the prize of any other participants does not change. Thus, the delegation leaders representing different countries do not compete against each other. This is a very important point.

You may ask: what about a team classification? The answer is very simple: such a classification does not exist. The IPhO is a competition between individuals only. There is no team result. Nevertheless, some people try to establish a kind of unofficial team classification. Some of them take a direct sum of scores as the result of the team. Some of them take the sum of scores of the three best participants in each team. Some of them take, for each team, the tree best results in each problem independently and so on, and so on. Of course, the final table depends on the method of calculating the team results, and probably one can always find some strange system of counting the team results that will show a team to be the best or one of the best ones. Non-existence of team classification is important. We do not wish to introduce rivalry between nations.

The financial principles of the organisation of the competition are the following:

Recently the International Board considered several times different proposals aiming to introduce certain participation fee. Taking into account different financial possibilities of different countries, in 1997 a voluntary fee was introduced. It seems, however, that in the future the voluntary fee will be converted into an obligatory fee.

The number of participating countries is, however, continually increasing. In 1999 62 countries were present (Table 1). Every year new countries join the competition and organisation of the competition becomes more and more expensive. Moreover, it is more and more difficult to organise the experimental part of the competition so that all the students have the same experimental conditions of work.

We can ask: what will be the maximum number of countries? How long can the number of participating countries increase without any changes (assuming the same structure of the competition)? Should we start thinking about "Olympiad Villages"?

Until now the organisers were always able to solve all the organisational problems related to the increasing number of participants. Some time ago I was sure that the maximum number of countries present at a given Olympiad would not exceed sixty. But in the meantime certain political processes took place, such as the break up of the Soviet Union, the break up of Yugoslavia, etc. In consequence of them many new countries were created. Most of them are interested in participation in the IPhO. Now it seems that the number of countries really interested in the IPhO shall not exceed eighty or ninety. Eighty countries with five students from each country, comes to 400 experimental stands. This is a very great number. Some countries, however, are able to provide such a number of identical experimental stands. Other countries can organise the experimental problem in two groups.

Can this number, i.e. 80-90, be reached? Theoretically, yes. But practically, probably not. The travel expenses (and possible participation fee that may be introduced in the future) can limit the number of participants. Many countries may not be able to send their teams to the competition every year for financial reasons. The number of participating countries will probably oscillate around eighty, depending on where the organising country is situated. This will not require "Olympiad Villages".

Organisation of the IPhO is becoming increasingly very difficult. The difficulties are diverse. I am not going to describe all of them. Nevertheless, I would like to give one simple example: languages. The marking of the solutions (written in national languages) is performed by the Organising Committee which is responsible for correct translation. For the languages spoken by a number of countries, such as English, German, French or Spanish, there are no serious difficulties. Also there are no difficulties in the case of nations or countries with a great diaspora (e.g. Poland). But in the case of certain minority languages (e.g. Finnish, Icelandic, etc.) the organisers sometimes face great problems. Fortunately, all the possible mistakes made during the marking procedure can be corrected at the verification sessions with the delegation leaders, although sometimes this is time consuming. Nevertheless, the problem of languages seems to be very difficult and probably some changes in the Statutes will be necessary.

In the context of the above mentioned "saturation" effects related to limited possibilities of the organisers (financial and technical) and limited possibilities of the participants (travel expenses, possible participation fee in the future) it makes sense to consider an idea of regional physics Olympiads. This idea is not new. Some time ago the Balkan Physics Olympiad was created. It involved the, so called, Balkan countries in Europe. As far as I know at least three such Olympiads were conducted. In 1992 the first Iberoamerican Physics Olympiad was organised (in Colombia). It is a Physics Olympiad for countries speaking Spanish or Portuguese. Unfortunately, for other reasons (insufficient international co-operation, certain financial and organisational problems) the second such Olympiad was organised only in 1997 (in Mexico). Shortly before the Gulf War the Gulf Physics Olympiad (for the Arab countries situated at the Arab Gulf) was organised. As far as I know, until now four such Olympiads were conducted.

It seems that the Asian region was the only region without such initiatives. I am absolutely sure that in the near future an Asian Physics Olympiad will be created. I am also sure that the educational role of such an Olympiad for this region will be extremely great as all such events strongly affect education. Additionally, this kind of peaceful co-operation creates better understanding between countries and between people, especially between young people who will decide about our prosperity in the future.

The competition tasks of several initial International Physics Olympiads were not overly difficult. They were similar to more difficult school tasks. Later the difficulty of the competition tasks was increased. It is not easy to measure difficulty of the competition tasks. I know two approaches to this problem.

First of them was made by G. S. Tarasiuk [1]. She defined a coefficient of difficulty k of the task as a quantity proportional to the ratio of the maximum possible score to the mean score gained by the participants. In a similar way she defined a degree of difficulty of a whole Olympiad. Her statistics involved ten first competitions. The quantity introduced by Tarasiuk seems to be quite good. It, however, cannot be applied to recent Olympiads since the International Board has decided that the results of the participants who have not received any prize or honourable mention cannot be presented publicly. In consequence the mean value of the scores gained by the participants is not known.

The second approach is due to Barbara and Rudolf Gau [2]. They introduced another parameter A as a measure of the, so called, requirement level. The definition of this parameter is too sophisticated to quote it here. Nevertheless, it seems quite interesting to show how the parameter A changes in time - Fig. 1 shows the dependence of A for twenty first International Physics Olympiads. Note the rapid increase in the period 1986 - 1989. (Unfortunately, nobody investigated A for more recent competitions.)

Fig. 1. Requirement level A (vertical axis) vs. no. of the Olympiad (horizontal axis).

One should realise that any way of measuring the "difficulty" of the Olympiads has only an approximate character. The best measure should involve such "parameters" as: formulation of the problem, length of the texts of the problems (sic! - some problems are unexpectedly long), possibilities of solving the problems in different ways, creativity of the problems, spectrum of knowledge tested by the problems, etc., etc. Each of these "parameters" in general is not well defined. Moreover, each of them should be taken with some weight, which is not well defined either.

As we have already mentioned, there is no official team classification - the Statutes of the Olympiads do not define any team results. Nevertheless, many countries participating in the International Physics Olympiads are interested in some measure of success of their teams over the years. Sometimes such a measure is necessary for them in order to estimate the efficiency of different forms of work. Of course, one may introduce different parameters describing "efficiency" of participation. Proper measure should involve difficulty of the competition problems, quality of grading, quality of translations, etc., etc. In general it is a very difficult problem. This is why we suggest (as a 0-th approximation) to use the parameter defined below the Table 3 [4]. The table contains the statistical data for thirty International Physics Olympiads organised until now (see also Table 4 and Table 5 ). Of course, in case of countries that participate infrequently in the competition, this parameter is not good for fluctuations.

The results of the competition are treated in different countries in different ways. In some countries, in some periods, they are or were treated as a kind of great national achievement: the participants pass a special, very intensive, training before the competition and later the winners receive great privileges. But it seems that such an approach is rather not typical. Most of countries treats the Olympiad as a kind of measuring instrument that measures the state of physics education. Of course, one success or lack of success has no special meaning. It may be a fluctuation. But successes or lack of successes for several years should be treated seriously. This is why the results of the competitions are analysed seriously. The same refers to the competition problems, the Syllabus, etc. In consequence of these analyses some countries improved their national syllabuses on physics by introducing new approaches (e.g. in thermodynamics), new topics (e.g. relativity, quantum physics), or by reducing some parts of too traditional character (e.g. geometric optics). Such changes are an additional result of the International Physics Olympiads, additional with respect to the tables of the competition winners. Certainly in a long term scale this result is more important than the names of the winners, as any improvements in the physics education affect all the pupils.

It is obvious that the existence of the International Physics Olympiads itself is a result of certain international co-operation. More important is a long term international co-operation between the members of the International Board. This kind of co-operation has existed since the very beginning, i.e. since the first IPhO. The members of the International Board exchange physics problems, books, journals, articles, they discuss their experience gained during organisation of the national physics competitions etc., etc. Due to such permanent, or semi-permanent, contacts and due to existence of the International Physics Olympiads some countries have organised national physics Olympiads or, at least, smaller scale competitions for selecting the teams to attend the international competition.

Nearly all the participating countries in the IPhO provide special training for the participants. Of course, too intensive training may deform the results. (After a long and intensive training even an elephant may dance to the tune of the piper, but certainly that has nothing to do with the natural abilities of the elephant and one may suspect that the elephant would not be too happy at that!). In consequence of an extra intensive training the results may not reflect real abilities of the students. Also they do not reflect the true state of the physics education. One should say, however, that most of the countries approaches to the problem in a rational way. The training periods etc. in different countries is presented in Table 6.

The impact of the International Physics Olympiads is continually growing. The role of the International Physics Olympiads is recognised also by such international organisations as UNESCO and the EPS (European Physical Society).

The first contacts with UNESCO took place way back, in 1968, but more extensive co-operation began in 1984. In the period 1984 - 1991 UNESCO supported financially the publication of the proceedings of the of the subsequent Olympiads. The proceedings were distributed to all the countries-members of UNESCO. It gave us favourable publicity. In addition, UNESCO has published several books on the physics Olympiads in various languages.

The help of UNESCO was very valuable, especially in propaganda. Unfortunately, its financial contribution to organising the competitions was negligible.

One should realise, however, that the purposes of UNESCO and other international organisations are not identical with the purposes of the International Physics Olympiads (although often many points are common). For example, by forceably increasing the number of participating countries one can cause very serious organisational problems. The organisers of the recent Olympiads encounter many difficulties of technical and financial character. To make the work of the organisers somewhat easier, in 1997 a voluntary fee paid by the participants was introduced. This fee covers part of the organisational expenses and is a good starting point for raising money from possible sponsors. In order to ensure smooth organisation, the increase in the number of participants in the International Physics Olympiad should be controlled. Otherwise organisation of the IPhO could collapse.

Like UNESCO, the EPS gives us very strong moral support as well as favourable publicity, and propagates our achievements among the countries-members of the EPS. It was the EPS that inspired us in preparation and publication of the booklet entitled Procedures for Selecting Teams to the International Physics Olympiads [3]. The booklet comprises a compilation of reports of different delegations and is very important and helpful for the countries wishing to join the competition. The booklet was prepared by the Secretariat together with Prof. Lars Silverberg and published by him privately in Lund (Sweden). In 1989 the EPS created an almost permanent special prize for the winner of the Olympiad for reaching the best equilibrium between the theoretical and experimental parts of the competition.

[1] Galina Seregeyevna Tarasyuk, Issledovanye mezhdunarodnych olimpyad po fizikye kak sredstva razvitiya sposobnostyei uchashchikhsya, manuscript of the lecture given in Varna during the XII IPhO (distributed among the delegation leaders)

[2] Barbara Gau, Rudolf Gau, On Alternations in the Structure and Requirement Level of Theoretical Problems Set in IPhO, "International Physics Olympiads - vol. I" (ed. by W. Gorzkowski), World Scientific Publishing Company, Singapore 1990, pp. 53 - 71

[3] Waldemar Gorzkowski, Andrzej Kotlicki, Lars Silverberg, Procedures for Selecting Teams to the International Physics Olympiads, publ. by L. Silverberg, Lund 1986

[4] International Physics Olympiads. - vol. I, ed. by W. Gorzkowski, World Scientific Publishing Company, Singapore 1990, pp. 126 - 127