You'd need 500% at least and by that point you've used like a quarter or fifth of your city to prevent the loss
We all know my numbers by now, so no need to re-post.
What Dursland says has merit.
I use my Watch Fires and Ritual Flames to fill in the gaps.
18 Goods buildings.
12 Supply buildings.
My tiny Military Complex of one Champs Retreat and One Rogue Hideout provide because of my Alcatraz.
In a few days or less, I enter Arctic Future.
That will give me more expansions and then I extend my main road, to increase Goods Production.
No loss of production here due to my City Defense.