While at AIMS, Theophilus studied the empirical modeling of the Ghanaian GDP was done by using the Box-Jenkins model which is also known as the Autoregressive Integrated Moving Average model (ARIMA).

After AIMS, Theophilus worked as a production analyst in a timber firm for a year and then obtained a MSc. in Mathematics at Hohai University in Nanjing, China. He Completed his PhD in 2021 in the same university and is currently a Postdoctoral research fellow at the University of Oslo, Norway.