Thanks Rap. Someone elsewhere pointed me to you answering this before.
Difficulty of contracts, non-contract locations and roaming parties scales differently.
Contract difficulty scales with time, the strength of your roster, the difficulty rating (skulls), the type of contract, and some factors specific to the type of contract – for example, escort contracts are generally more difficult the longer you travel, as it increases the chance to run into enemies. Renown does not factor into contract difficulty, but it does factor heavily into contract rewards; the more renown you have, the more you’ll be paid.
Difficulty of non-contract locations and roaming parties scales mostly with distance to civilization and time. Roaming parties also scale slightly with player strength, but less so than contracts, and non-contract locations don’t scale with player strength at all.