http://time.com/money/4748384/high-risk-insurance-pools/?xid=homepage

High-risk health insurance pools are back in the news after it was reported House Republicans are considering making them a component of their plan to repeal and replace the Affordable Care Act.

The GOP is toying with the idea of allowing states to seek a waiver to the ACA’s prohibition on charging sick people higher premiums if the states set up high-risk pools. Insurers would still be prohibited from denying people coverage outright, but they would be able to jack up premiums for people with a range of conditions and illnesses, effectively pricing them out of the individual market. Instead, people with pre-existing conditions—which ran the gamut, from cancer to high blood pressure, in the pre-ACA days—would be segregated into “high-risk pools.”

Many states had these pools in place before the passage of the ACA, and research showed that they did not keep costs down. So what exactly are high-risk pools, and why didn’t they work before? Here’s what you need to know.