Table 3.

Prior and current study methods and results comparison.

Study	Well/facility inventory limits	Well parameters	Apportionment	Buffer (m)	Count type	Reported results	This study
						(million people)
Gold and McGinty (2013)	Unconventional	Spudded or produced after 2000	Complete apportionment	1,600	11 top-producing states (Texas, Ohio, Pennsylvania, California, Oklahoma, Louisiana, Colorado, Michigan, New Mexico, Wyoming, North Dakota)	15.3	4.03
					California	1.62	0.10
					Pennsylvania	1.78	0.33
Earthworks et al. (2016)	All wells plus processing plants and compressors	Permitted wells	Proportional apportionment	800	United States	12.4	8.89
					California	1.3	0.76
					Pennsylvania	1.5	0.96
Srebotnjak and Rotkin-Ellman (2014)	All wells	Drilled or newly permitted	Proportional apportionment	1,600	California	5.4	2.09
Ridlington et al. (2015)	Unconventional	Permitted between 2007 and May 2015	Proportional apportionment	1,600	Age 5 or under, Pennsylvania	0.03	0.02
				1,600	Age 75 or older, Pennsylvania	0.04	.03

Note: The column “This study” reports population counts from our well inventory, using the limitations criteria specified in the column “Well/facility inventory limits.” We limit population counts to those within proximity to unconventional wells when applicable. We did not include ancillary infrastructure. All other criteria used by other studies, such as the inclusion of permitted wells and inactive wells, are excluded from the population counts we provided, for comparison purposes.