In 2018, unsubsidized premiums for ACA-compliant individual healthcare policies have shot up by around 30% on average nationally. Around 18 points of this (60% of the total) is due specifically to policy decisions by the Trump Administration and Congressional Republicans, primarily the cut-off of Cost Sharing Reduction reimbursement payments and the (accurate, as it would later develop) anticipation, by some carriers, of the ACA's individual mandate being repealed.
What about 2019, however? The 2-3 points tacked on out of concern for the mandate being repealed was only a small portion of the full impact insurance carriers expect it to have, and of course there's the further undermining of the ACA via Donald Trump's "Short Term" and "Association Plan" executive orders. Finally, there's the impact of what is assumed to be another year of the advertising/outreach budget being starved by the Centers for Medicare & Medicaid.