Right. I noticed that. They're assuming that drones are distributed randomly across the entire volume of US airspace. The analysis isn't based on data from pilot reports. The FAA tallies drone sightings from aircraft, and for 2015, they had 650 reports through August 9th.[1] That's a lot, considering that seeing a small drone from an aircraft means it is rather close.

Drone reports are available online.[2] Most of the reports are from near airports. Here are a few months of reports from LAX alone:

PRELIM INFO FROM FAA OPS: LOS ANGELES, CA/UAS INCIDENT/091658P/LOS ANGELES ARRIVAL REPORTED SOUTHWEST 366, B737, REPORTED SEEING AN UNIDENTIFIED HELICOPTER AT 4,000 FEET WHILE ON A 6 MILE FINAL TO RUNWAY 24R. LOS ANGELES PD AIR SUPPORT ADVISED, LOS ANGELES PD 18 RESPONDED.

PRELIM INFO FROM FAA OPS: LOS ANGELES, CA /UAS INCIDENT/1821P/SOUTHERN CALIFORNIA TRACON REPORTED SOUTHWEST 366, B737, OBSERVED A QUADCOPTER TYPE UAS AT 4,000 FEET 6 MILE FINAL LAX. LAPD AVIATION UNIT NOTIFIED.

PRELIM INFO FROM FAA OPS: LAX/UAS INCIDENT/0815P/LAX ATCT ADVISED COMPASS 5680, E170, SEA-LAX, REPORTED UAS 200 FEET ABOVE ACFT ALTITUDE OF 600 FEET OFF RIGHT WING WHILE ON 2.5 MILE FINAL RWY 24R LAX. LA CO SHERIFF NOTIFIED.

"PRELIM INFO FROM FAA OPS: LAX/UAS INCIDENT/1625P CESSNA C525 OBSERVED AN REDDISH-ORANGE-YELLOW COLORED UAS, MODEL UNKN, WHILE SOUTHBOUND AT FL200. NO EVASIVE ACTION TAKEN.

"PRELIM INFO FROM FAA OPS: LOS ANGELES, CA/UAS INCIDENT/1357P/LAX ATCT ADVISED UNITED 701, B757, PAX REPORTED TO PILOT SEEING A UAS TURN TOWARDS ACFT ON LEFT SIDE WHILE ON FINAL RUNWAY 24R, 2,000 FEET.

Summary: POSSIBLE DRONE SIGHTING: UAL701 (B757), LANDED RY24R & LATER CALLED LAXT ON AN UNRECORDED LINE TO REPORT WHAT 2 PASSENGERS ADVISED HIM: ON 6-MILE FINAL TO RY24R, THE PASSENGERS CLAIMED TO SEE A DRONE BTWN 2000' - 2100' BTWN RY24L & RY24R TURN TOWARD THE AIRCRAFT; NO INJURIES REPORTED.

"PRELIM INFO FROM FAA OPS: LOS ANGELES, CA/UAS INCIDENT/2017P/UNITED 1600, B737, REPORTED SEEING A UAS FLY ABOVE ACFT AT 2,600 FEET 8 E LAX. LAPD AVIATION AIR SUPPORT WAS NOTIFIED AT 213-485-2600. NO EVASIVE ACTION TAKEN.

Summary: DRONE REPORT, UAL935, B772, ON FINAL RY25L. UAL935 REPORTED A DRONE OFF THEIR LEFT SIDE ON APPROXIMATELY A 1 MILE FINAL AT 300-400FT. PILOT, CAPT. JEFF GLEASON, RPTS WHITE QUAD DRONE (ABOUT THE SIZE OF A MEDIUM PIZZA BOX), STATIONARY JUST WEST OF THE 405 PASSED JUST UNDER THE LEFT WING. NO EVASIVE ACTION TAKEN. DEN NTFD.

PRELIM INFO FROM FAA OPS: LOS ANGELES, CA/UAS INCIDENT/0851P/LAX ATCT ADVISED JET BLUE 23, A320, REPORTED A WHITE UAS ON THE LEFT SIDE OF THE ACFT WHILE WSW BOUND AT 500 FEET 1 E LAX. NO EVASIVE ACTION TAKEN. LAPD AERO BUREAU NOTIFIED.

Summary: DRONE REPORT FROM JBU23 (A321) 1 MILES EAST OF LAX, LEFT (SOUTH) OF RY25L FINAL @ 500 FEET, STATIONARY WHITE DRONE, NO EVASIVE ACTION, LA COUNTY SHERIFF AERO BEREAU NOTIFIED @ 1610Z, DEN NOTIFIED @ 1611Z.

That's just LAX. The distribution of reports is nowhere near random. In addition to airports, drones have been reported near stadiums; one crashed into a spectator.

The paper is from George Mason University's Mercatus Center, which is a right-wing "university source for market-oriented ideas." The authors are economics students. It's not from anybody involved in aviation safety.

[1] https://www.faa.gov/news/updates/?newsId=83445
[2] https://www.faa.gov/news/updates/?newsId=83544