Spencer wrote that in production the advantages of the superior individual are comparatively minor, and thus acceptable, yet the benefit that dominance provides those who control a large segment of production might be hazardous to competition. Spencer feared that an absence of "sympathetic self-restraint" of those with too much power could lead to the ruin of their competitors. He did not think free market competition necessitated competitive warfare. Furthermore, Spencer argued that individuals with superior resources who deliberately used investment schemes to put competitors out of business were committing acts of "commercial murder". Carnegie built his wealth in the steel industry by maintaining an extensively integrated operating system. Carnegie also bought out some regional competitors, and merged with others, usually maintaining the majority shares in the companies. Over the course of twenty years, Carnegie's steel properties grew to include the Edgar Thomson Steel Works, the Lucy Furnace Works, the Union Iron Mills, the Homestead Works, the Keystone Bridge Works, the Hartman Steel Works, the Frick Coke Company, and the Scotia ore mines among many other industry related assets. Furthermore, Carnegie's success was due to his convenient relationship with the railroad industries, which not only relied on steel for track, but were also making money from steel transport. The steel and railroad barons worked closely to negotiate prices instead of free market competition determinations.