Not available on all game worlds. Industry Shares are currently not a regular feature in Rail Nation. At the moment they are only available on selected special game worlds. On all other worlds, you will not see Industry Shares.
Industry Shares replace the Majority system for factories, harbours, and warehouses. Instead of one association holding exclusive control over an industry level, multiple associations can each unlock a share for the same level at the same time and all benefit from it.
Shares apply to a single factory/harbour/warehouse level, not to the whole industry. A share must be unlocked separately for each level.
Association members jointly contribute money toward that level's funding goal. Contributions can be made in a fixed value using +/– controls, or by entering an amount directly; a single contribution is capped at what's still needed to reach the goal.
Once the goal is reached, the share is unlocked: every member of that association gets a bonus to waiting times in that industry.
Multiple associations can hold a share for the same level at the same time — ownership is not exclusive.
Contributions beyond the current level's requirement count toward the next level's share, so associations can secure a share for a future level in advance. If requirements for the current level are not met, the already contributed money keeps carrying forward until enough money is invested to unlock a new share.
Personal investments still work as before: they give a personal waiting time bonus and still generate prestige for the top investors.