Our experience suggests that most firms have the resources to really target a limited number of sectors, perhaps two to five, depending on size and reach. (lawpracticetoday.org)
And it has been focused on a relatively small number of sectors, mainly «general environment protection» and «energy». (sei.org)
Or, you could choose a somewhat arbitrary number of sectors, and a desired allocation based on an arbitrary acceptable «balance» level. (canadiancapitalist.com)