When you own two or more strategic business of the same kind on different markets, they will create business synergy, which gives an extra boost to the business.
If you want to improve the synergy of specific strategic business, you can try to expand to a new market that also has the specific business. For instance, if you have expanded to market “Middle Asia” and own the strategic business “Oil”, you could next try to expand to “Middle East” or “Russia”, because both markets have also “Oil” business. To study where to find more of a certain kind of strategic businesses, open the desired business details view.
Once you own several strategic businesses of the same kind, you should level them up, because the combined number of business level ups improves the business synergy. Simply higher the total number of level ups, bigger the boost will be. Reaching certain thresholds with combined level ups will give even bigger boost. To study this more, open the details view of the business and check the business level up indicator in “Business synergies” section.