In the many things to dissect about the Affordable Care Act (ACA), one thing we will study is the decisions by states not to operate their own Marketplaces, and states not adopting Medicaid expansion. 

Given the problems to date with the federal website, it is notable that this likely has hampered many people in the 36 states not operating a state marketplace.  One measure of this is that of the 993,635 people who applied for coverage in the state marketplaces, only 21% were enrolled in marketplace or Medicaid plan by 11/2.  In contrast, 57% of the 516,248 who applied for coverage had enrolled by 11/2 in the 15 states with state Marketplaces.

This suggests enrollment would be a lot higher now if everyone were operating a state based Marketplace.  One measure of this is that roughly 352,000 more people would have been enrolled if every state had the average efficiency of the state based Marketplaces.  So instead of reporting that 502,446 were enrolled on 11/2 we'd be reporting that 855,000 were enrolled.

There are likely several ways to compute an estimate like this, and the numbers would differ if different assumptions were used, but the general point still applies.