Exclude specified filter

I have a dataset that is a combination of headcount and transactions (i.e. terminations, promotions, etc). One of the ways the terminations are categorized is by a detailed action reason.

I want to be able to filter turnover rate (# of terminations / average headcount) by the detailed action reason. In order to do this I need to ignore the all filters on the headcount calculation, except for the detailed action reason filter.

Using this formula:

Turnover Rate =

DIVIDE( [Total Terminations],

CALCULATE( [Average Employee Headcount], ALLSELECTED() )

I was able to ignore all filters on the headcount calculation to get an average headcount that would look something like this:

It is the same for all years, action reasons, etc.

But I only want to ignore the detailed action reason filters and keep every other filter. For example, if I were to filter on year and detailed action reason I would want it to look something like this:

What can I use to exclude just the one filter (in this case Detailed Action Reason), while keeping the rest?

Here is the calculation for the Average Employee Headcount measure for reference:

Average Employee Headcount =

DIVIDE(

CALCULATE(

COUNT(data[Employee ID]),

data[Action Type] = "Headcount"),

CALCULATE(

DISTINCTCOUNT(data[Effective Date]),

data[Action Type] = "Headcount")

)