refore, the software developed for telecom purposes may be marketed in these industries, too. As a result, the increased total pool of customers will allow a larger number of vendors to co-exist. The ratio of the actual number of vendors in the market to the estimated maximum number (v/ max V E [0, 1]) may be used as a measure of market con- centration and competition as a software market competition index: if the ratio is close to 1, the market is considered to have a high level of competition. Given 42 vendors acting in the mediation segment, we obtain v/ max V = 42/46 = 0.91. This would indicate the market being relatively competitive. A calculation of the Herfindahl-Hirschman index (HHI index) - commonly used for assessing market concentration - for the mediation segment confirms this result. The HHI for the mediation segment is 704 for the year 2006. The mediation segment can thus be concluded as being unconcentrated and competitive, and this is in line with the above calculated competitiveness share of 0.91. Market Polarization due to Difference in Interface Implementation Efforts Oleksiy Mazhelis and Pasi Tyrväinen Another factor potentially affecting the evolution of the OSS/BSS software market is the high complexity of software interfaces. The software provided to a customer - a CSP - needs to be integrated with a number of heterogeneous subsystems deployed by the customer. If the number of integration interfaces is high, a vast amount of special knowledge is needed in the vendor organization. High integration efforts also take up the time of the compentent employees of the vendor organiza- tion, thereby reducing the number of customers which it is capable of serving. As a result, only few large vendors can compete in such market, and, due to a lack of competition, the evolution towards a horizontalized market with standardized interfaces and established standard architectures may be delayed or may never take place. In this section, we shall consider whether the high complexity of the OSS/BSS software in