2.2.4 Comparison with single operator deployment It can be debated whether co-investment models are superior to deployment by a single network operator that receives government incentives. If the single network operator is required to provide open access to other operators on a non-discriminatory basis, at cost-oriented prices, then co-investment alternatives may not be materially better. After all, It is likely to be easier to implement a bilateral arrangement between the government and a single network operator (usually the incumbent in the fixed sector), for a speedy network roll-out.On the other hand, the burden to regulate the incumbent operator will persist and may even intensify with the single operator model. If the single operator participates in the downstream retail market, there will still be an incentive to engage in discriminatory behaviour favouring the operator’s retail activities. All of this suggests that a sharing arrangement is more likely to lead to a reduced regulatory burden as compared to a single network operator model.2.3 The development of network sharing models This section explains how network-sharing arrangements developed and evolved in both the mobile and fixed-service sectors.2.3.1 Evolution in the mobile sector Commercial network-sharing arrangements have been prevalent in the mobile sector, both in developed and emerging markets. These arrangements mainly developed voluntarily between mobile operators, with only fairly light-touch encouragement from governments. Today, approximately 15 per cent of mobile operators engage in some type of network sharing.Mobile network sharing is commonplace when powerful competitive pressures make it necessary for operators to reduce costs. This usually arises in mobile markets where there are four or more network-based competitors. In these markets, there has been substantial passive sharing and increasingly active sharing, including through the use of third parties such as tower companies or \"towercos\".Sweden was one of the earliest countries to take up mobile network sharing and it appears that these arrangements have been enduring (see Box 2.1).Australia was also one of the earliest countries to adopt mobile sharing arrangements. For various reasons, however, these arrangements did not survive for very long (see Box 2.2).Most of the cost savings from network sharing (up to two-thirds) can be captured by sharing passive infrastructure. The cost savings from sharing active infrastructure are not as great, but they are still sizeable – delivering approximately 20-30 per cent cost savings for mobile networks. An approximation of cost savings from different types of mobile infrastructure sharing is shown in Figure 2.1.The pressure to share mobile network infrastructure is heightened by the explosion in consumer and business demand for data. Data is a lower-margin business compared with earlier voice and messaging services. At the same time, the cost of running inefficient legacy networks is greater when dealing with high data volumes. New LTE networks, which are optimized for carrying huge volumes of data, involve major new investments by operators.\"Green-field\" situations that require entirely new networks are generally considered to be easier and more suitable for sharing. This is one reason why network-sharing deals are more frequent in emerging markets than in developed ones. Although there is some sharing of existing assets, LTE is a more green-field opportunity, and this boosts the chances of a successful LTE network-sharing deal.Trends in Telecommunication Reform 2016 57 Chapter 2