This paper presents a novel simulation method for estimating the likely welfare effects of policy reforms aimed at increasing competition in strategic economic sectors such as mobile phone services. The proposed method relies on a partial equilibrium simulation approach and estimates the welfare impacts on current consumers and the potential welfare effects among new consumers brought into the market by changes in prices due to competition. This approach is applied to the information and communication technology (ICT) sector in Ethiopia, one of the three countries in the world with a monopoly in the market for mobile phone services. Based on household budget survey data for 2015/16 and departing from a baseline reform scenario that dilutes the market share of the state-owned monopoly to 45 percent, the simulation model estimates a 25.3 percent reduction in the price of mobile services and an increase in 5.7 million new users of mobile services. The predicted drop in prices and increased users would generate a combined relative welfare gain of 1.18 percent (1.09 percent among current users and 0.09 percent among new users), that could be translated into a 0.31 percentage point decline in the national poverty rate and equivalent to lifting about 275,000 people out of poverty. Alternative reform scenarios that dilute the market share of the monopoly to 75 percent and to 30 percent are expected to reduce poverty rate in 0.13 and 0.52 percentage points, respectively. The method proposed in this study represents a useful tool for promoting competition reforms in developing countries, particularly in sectors known for excluding significant segments of the population because of high consumer prices.