Faction dividends are accrued based on the ratio of credits in the faction treasury and the faction profits from structures. The better this ratio, the higher the dividends will be. This ratio is higher when faction structures have surplus credits on-hand that are not profits, such as from rounding or appreciation of stock, these credits are added to the treasury as profits increasing the ratio; but 2% is aways withheld as faction dividends.
You can disperse dividends as a founder to all faction members by visiting a faction system with a treasury. Open the services window, select faction treasury and then press the disperse button.