The characteristics of the developing market to which the Serbian market belongs are: illiquidity, low turnover and nontransparency. The aim of this paper is to examine the possibility of application of the Markowitz's model for forming the set of efficient portfolios on the capital market in Serbia. The research is based on previous theoretical and empirical research in the world. Statistical methods of determining return and risk, matrix of variances and covariances for liquid shares have been applied. Portfolio optimization has been conducted by add-in programme Solver included in the Microsoft Excel package, respecting the limitations according to Markowitz's model. The results of the analysis have shown that the set of efficient portfolios, which meets the criterion that they give minimal risk for the given return, can be formed on the capital market in Serbia. The results show that Markowitz's model allows the investors to select the efficient portfolio, but only for liquid shares, depending on the risk they are ready to accept. The findings of this paper indicate that expressive illiquidity on the Serbian market and insufficient number of shares for diversification by sectors make the practical application of the research results difficult.

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Abstract:The starting hypothesis is that the market structure to a large extent determines the conduct and the level of the achieved performance of economic entities. The aim of this paper is to determine the theoretical and empirical correlation between market structure, conduct, and performance of economic entities. The paper provides an analytical overview of the mobile telecommunications market in the Republic of Serbia. By using different indicators (the Concentration ratio, the HHI, the Lorenz curve, and the Gini coefficient), the supply concentration in this market is measured and the nature of competition is analysed. By using statistical methods (correlation and simple linear regression analysis), the correlation between the variables, which confirmed the existence of a strong positive correlation between the degree of supply concentration on the market and the level of achieved performance is examined.

Agreed upon by the United Nations, the seventeen Sustainable Development Goals (SDGs) set out a framework to tackle the world's most pressing social, economic, and environmental challenges in the lead-up to 2030. They provide a network to support business in managing risks and identifying market opportunities. The Sustainable Development Goals have the potential to accelerate innovation and economic growth. However, the ambitious goals will require new models of collaboration between companies, sectors, countries, and regions. The special attention in this paper is given to the analysis of the achieved results in the Western Balkan countries in 2018 measured by the composite indicator such as Sustainable Development Goals Index. The basic research question in the research is: Are all the Western Balkans countries lagging behind the average of the region Eastern Europe and Central Asia in achieving the sustainable development goals? Key words: sustainable development goals, index, Western Balkan countries JEL classification: Q53 циЉеви одрживог раЗвоја и остварени реЗултати у ЗеМЉаМа Западног Балкана апстракт Договорени од стране Уједињених нација, седамнаест циљева одрживог развоја (СДГс) поставило је оквир за решавање најзначајнијих друштвених, економских и еколошких изазова до 2030. године. Они пружају мрежу подршке пословној заједници приликом управљања ризицима и идентификовања тржишних прилика. Циљеви одрживог развоја имају потенцијал да убрзају иновације и економски раст. Међутим, амбициозни циљеви одрживог развоја ће

The main purpose of the paper is to address the effects of digital transformation in the telecommunications markets which are characterized by network externalities. By acknowledging disruptive effects of digital transformation age, the paper highlights challenges which were created by advancement of technological capabilities. The specific aim of the paper is to present a methodological framework for measuring the information society. The research will be based on an analysis of the number of subscribers by types of telecommunication services, in developed and developing countries, in the last two decades. In this regard, increasing the number of subscribers leads to higher value of the selected network. We expect confirmation of both hypotheses respectively (H1: Digital transformation affects the simultaneously continuous growth of the number of subscribers and the continuous decline in prices of telecommunication services; H2: There are similar trends in developed and developing countries, which are related to the number of the telecommunication services subscribers). Therefore, digital transformation and the effect of network externalities contribute to increasing the number of subscribers, reducing the number of networks (distortion of the market competition) and reducing the prices of telecommunication services.