Q: How do I increase development in my provinces, what does encourage development mean?
A: The development system in DG models population. if a country has 75 development, that means it has roughly 1 million population. This is not the same case for individual provinces, and instead a formula is used to determine province development, as to avoid certain provinces, like Beijing and Tokyo, having disproportionate effects do to their development. Because of this, you are unable to manually increase development, and instead an event will fire, increasing the devlopment in a province by 1. This event has different MTTH for different terrain, and is modified by a number of things.
Terrains and their Dev Growth MTTH:
- Farmlands (300 months MTTH)
- Grasslands, Drylands, Woods, Coastline, Savannah, Highlands (600 months MTTH)
- Forest, Steppe, Hills, Marsh, Mountains (900 months MTTH)
- Jungles, Coastal Desert (1600 months MTTH)

Dev Growth MTTH Modifiers:
- Encouraged Growth = 0.5 multiplier (halves the time taken for dev to increase)
- Center of Trade = 0.95 multiplier, per level, so a level 3 will have a 0.86~ multiplier
- Development of the Province = 0.95 multiplier, per 10 development, up to 50 development
- Industrialisation Institution Embraced = 0.75 multiplier
- Government Rank = 0.95 multiplier, per rank, limited to the capital province
- Equivalent Building Type = 0.95 multiplier. Barracks, Training Fields for manpower, Workshop/Counting House for production, Temple/Cathedral for tax

This question, and more, are answered on the Dei Gratia discord in #mod-info