How do trade agreements affect traded items' price and availability?

I'm currently trying to purchase a lot of Steel items from the dwarven caravans to melt. Hence, I've pushed the demands for all items that can be made of steel (minecarts, cages, crafts, etcetera) to the max. This increases prices for the items, as indicated in the trade agreement. However, it doesn't grant that the caravan will actually bring those items, and if it brings, their prices will be inflated by demand and by quality. So, I ask the following (related) questions:

1. Does an increase in demand translate (linearly) to an increase in the dwarven caravan's offer?
2. Does the same increase affect the quality of items offered?

If an increase in demand doesn't translate directly to an increase in offer, and instead translated to an increase of the current offer of higher-quality items, it would be economically saner to not increase demand.

If you set goods on higher priority the caravans will bring more of those goods. You will pretty much overflow in the goods you put on highest priority once the caravan visits you again.

Obviously the price increases too, i never seen a significant increase in quality however. It might even be lower, maybe because the other traders put lesser skilled workers on the job. I did not do any !science! about the quality though. I guess it might look like you see more higher quality stuff since the caravan brings more of that type. Maybe there is somekind of hidden mechanic that they will sell there legendary stuff only when you drive the price up, that remains guessing until some significant !science! has been done i suppose.

I do think it is linear (but one can only speculate, however everything in the game is randomized so it won't ever look linear until a lot of !science! has been done. The first year they could bring 5 steel items, the next year without increasing demand it could be 50. If you would increase demand the next year they would bring much more by your theory. However there are very possibly some base numbers on what to bring. These numbers probably increase linearly, see it like this:

• Toys 100%
• weapons 100%
• Armor 100%
• Food 100%

Now if i would give you 12 of these items randomly, each with the same amount of chance % you could end up easily with 4 toys. If i would give you 20000 of these items randomly you would get around 5000 of each. So if you increase demand by 200% for an item your chances of getting that item in the long run increase significantly:

• Toys 100%
• Weapons 200%
• Armor 100%
• Food 100%

Now if i would give you 20000 of these items you would get around 8000 weapons and 4000 of the other three.

But the basic idea is if you need steel you should request steel. The price does not really matter, if you smelt a couple of steel toys and make them into some nice weapons, armor or trap components you will earn your money back more then a couple of times. Dwarfs can get rich fast you know.