It’s a “control premium”. The way the theory explains it is that you are making an offer to acquire control of the company, so you pay a control premium above what others are willing to pay on normal transactions in the market. In practice, how big of premium the acquirer pays is influenced by considerations specific to the history of the company, the shareholder base, its share price history, etc. …but theory and practice do link together, and you can trace the historical trend of control premia paid have changed over time, or even how they change from country to country.