Why am I losing population?

No natural disasters or wars recently however I do purchase population from time to time and my health index is 121

Need to take something like this to the "help" or even "beginners" forum. Providing your country name and world you are on would not hurt either.

Your people think you smell and are moving upwind.

Johanas Bilderberg is correct. You may be able to combat this by investing in smellier corporations (cheese, sulfur etc). Your workers should not leave if they are themselves equally pungent.

In seriousness though, your population of 100,000,000 is above the game 'norm' threshold and will experience gradual natural decrease.