Employee Turnover and total headcount

Hi Guys,

I hope someone can help me. Im relatively new to power BI and im creating a dashboard for our HR department. 

I have an excel sheet where i have all the data required and i would like to calculate employee turnover on a yearly basis. 

The data i have is as follows;

-Active (Y/N)

-Hire date

-Termination Date

 how can i show turnover percentage every year using this data.

- I also have another problem, when i use the card visualization to show our current headcount and then filter the headcount by year, the filter only shows the (new Hires of that year and not the total head count of that year) Like for eg; Say our current headcount is 5000 employees and it is displaying 5000 without filters, then once i filter it to the year 2013, the overall headcount as of 2013 is 2000 people, however its only showing the New hired employees of 2013 which is 400.

how do i change it to show the total every year? 

thanks