I have a table DepartmentChanges that looks something like this.

I want to get a query of the net change in department size. The way I am currently doing it feels hamfisted and I have this itching feeling that there is much simpler way to do this. (there is enough coverage that the left join works and no full outer join + coalesce(countfield,0) is necessary to prevent errors).

with cte1 as (
select Newdept, count(*) NewDeptCount
from DepartmentChanges
group by NewDept
),
cte2 as (
select PreviousDept, count(*) PrevDeptCount
from DepartmentChanges
group by PreviousDept
)
select NewDept, (NewDeptCount - PrevDeptCount) as NetChange
from cte1
left join cte2
on cte1.NewDept = cte2.PreviousDept

And the output looks like

Bonus points for being able to just pull in the DepartmentChanges table into powerbi and performing this in there.