This minor investment boom in the sector has not affected all economies equally, so there are still countries with supply problems owing to low investment in capacity. While privatization was complete in Chile, other countries stopped halfway (Brazil and Colombia), others opened the sector to private capital under a single-buyer model (Costa Rica and Mexico), while some, such as Uruguay, maintained the vertically integrated monopoly (Altomonte, 2002). This helped the development of privately owned Chilean firms which, as from 1992, took advantage of the reforms in other countries in the region to invest in them. This regional network made ENERSIS highly attractive to transnational corporations which were looking to expand in the subcontinent in the late 1990s. In 1999, the Spanish firm Endesa made a full takeover of ENERSIS S. A., and in the following year, the United States firm AES purchased Gener, another Chilean firm in the sector (see point 1 of section D).