Here are some resources for you but feel free to do your own research and find more information on the internet. Please cite your references.
https://www.cbo.gov/about/products/budget-economic-data#6 (Go to ’10 Year Economic Projections’ at the bottom of the page and click on the most recent date. An excel file will open. Go to ‘Calendar Year Data Release’ and find Line 30 for Natural Rate of Unemployment)