Re: OMG! a 1,000 percent increase....
There are several problems with the study, and you don't need to be a cynic for the study to red-flag itself.
The term "ghost gun" originally referred to any firearm manufactured before the October 1968 law that required all guns imported or manufactured to have them -- and still does. While most of the "ghost guns" seized may be 3D-printed garbage that is more hazardous to the one holding it than the person standing downrange, we really don't know the ratio to old/new guns or whether 3D printing was involved at all.
The fact that a gun was recovered as part of a crime investigation does not mean that it had anything to do with the alleged crime - and I say alleged because they count weapons from people who had them legally as well as illegally, from situations where no charges were filed after investigation, as well as from situations where the only crime was a prohibited person being in possession of the firearm without any immediate intent to use it illegally -- all while trying to inflate the numbers of "gun crime".
Readers in the UK who are familiar with their system of filtering spent convictions may be surprised to learn that in the USA, people who were once convicted of a minor felony, even if the crime was nonviolent and occurred decades ago, do not get their records expunged or filtered. Their debt to society is never considered paid in full. Even after their sentence has been served, they are permanently barred from certain civil liberties, including the right to own weapons. However, those people may feel the need to protect themselves and their family from violent criminals, and thus they acquire and possess weapons illegally.
Confiscation from these prohibited persons is a significant contribution to the study numbers. For these prohibited persons, even pepper spray can be considered a banned weapon and carries the same penalty as having a gun, so 3D-printing a weapon at home so that they aren't forced into the black market to buy one is a potent driver. Just to highlight the scope of this issue, recognize that in the United States a full 33% of all adult black males have felony convictions on their records and fall into this class of prohibited persons.
Of course, the so-called study was from Everytown, so you already know it's just a piece of political propaganda. History has shown us that they would rather lie than tell the truth, even when the truth would support their politics.