How Much Change in Income for Qualifying Event?

I am told that a substantial change in income can trigger as a qualifying event allowing enrollment in a new plan. Does anyone know exactly how much of a change is needed to qualify for this? Of course the fine folks at healthcare.gov were useless in helping me find this info

I didn't find the right solution from the Internet.

References http://www.insurance-forums.net/forum/health-insurance-ancillary-benefits/how-much-change-income-qualifying-event-t89850.html

Explainer video