Many products go through surpluses and shortages, the two you mentioned both tend to be in shortage more often than not because Carbon as a mining product is limited to premium players and having limited availability in each country. Electric Car Motors similarly can reach big shortages because they require Metadium as a supply product and it can only be sourced from Tiny Atlas world and sold manually on the markets on the core 5 worlds.
Take a look at the current supply and demand for each on your world, and assume that orders tend to be fulfilled in a 'first come first served' manner to plan out your ordering.
For example on White Giant, Carbon currently has a supply of ~ 21M units and demand of ~ 314M units of Carbon. So if you placed an order now, you would reasonably expect it to be fulfilled in 314M/21M -> 15 game months. So if you adjust the low level marks and order quantities of your corporations that use Carbon to compensate for market shortages, you can more than often than not make sure that they are always fully supplied outside of oddball products.