Regression to find out the impact of the Brexit vote on migration (pre-Brexit)

Hello and happy new year,

I have a minor in statistics and am having some trouble finding the right variables for my regression. I know that you need 1 independent variable and 1 or more dependent variables. For example, you could calculate what effect the independent variable "income" has on the dependent variable "happiness". To find out whether the Brexit referendum had an impact on migration figures, I could take "net migration", "immigration" and "emigration" as dependent variables. In this case, what would be the independent variable that would represent the referendum? Is that even feasible?

(The period studied should be from 2016 to 2019, but one can also look at the two years 2014 and 2015, for example, to see if there was a significant fall in 2016 compared to the previous period.)

Would regression be the right method here to find out the impact? Maybe someone can help me further :)

Best regards