You raise some interesting points concerning the relative contribution of different sectors of the economy for future growth. Agribusiness incubators are a major focus of the World Bank's work, as you would see, for instance, in the Agribusiness Innovation Sourcebook, or infoDev's Agribusiness Innovation Program (see: http://www.infodev.org/agribusiness). The infoDev study on mLabs and mHubs, cited in the blog, and the GSMA study (at: http://www.gsma.com/newsroom/digital-entrepreneurship-in-kenya-2014/) provide some preliminary findings on the contribution of the tech hubs to economic growth. The example of Kopo Kopo, which was incubated at the mLab East Africa before outgrowing that space, which was cited by another commenter, is a good example of a high growth company that has emerged from a tech hub. But it will take some time to judge the long-term effects of what is a relatively recent phenomenon.