When you have the market view open with a list of its businesses, tapping any part of a business row except the action (buy, upgrade, or level up) button will open a business details view.
The details tell you the name, level, current earn rate as well as the earn rate improvements that the next upgrade and level up will result. The details view has a section “Business synergies” with mini map. The mini map shows in which markets the business is available. For owned strategic businesses the map also shows the levels of businesses in different markets. Under the map is an indicator showing the combined number of the business levels, which impacts the boost. Each business level up improves the boost and reaching a specific threshold level will give even bigger boost. Also, strategic businesses that are more common (such as “Tourism”) have more threshold levels that yield higher boosts.