In December 2015, the web site TruthStreamMedia.com published an article claiming that (as of December 2015) there have been “more mass shootings under President Obama than the four previous Presidents combined,” as well as a much greater incidence of mass shootings involving eight or more victims:

Mass Shootings under the Last Five Presidents Ronald Reagan: 1981-1989 (8 years) 11 mass shootings

Incidents with 8 or more deaths = 5 George H. W. Bush: 1989-1993 (4 years) 12 mass murders

Incidents with 8 or more deaths = 3 Bill Clinton: 1993-2001 (8 years) 23 mass murders

Incidents with 8 or more deaths = 4 George W. Bush: 2001-2009 (8 years) 20 mass murders

Incidents with 8 or more deaths = 5 Barrack H. Obama: 2009-2015 (in 7th year) 162 mass murders

Incidents with 8 or more deaths = 18

TruthStreamMedia.com provided a PDF of their data as well as links to the various sources used to compile that information:

However, the sources listed by TruthStreamMedia.com did not back up their claims that a much larger number of mass shootings had taken place during the administration of Barack Obama than during the administrations of his four predecessors combined. TruthStreamMedia.com seriously fudged the numbers by applying different standards for “mass shootings” to the years during which Barack Obama has served as President.

The numbers for President Obama include many killings that are not considered “mass shootings” by common definition but are instead classified as “multiple homicides” or “mass killings” (including many instances of familicide, in which one person kills an entire family, typically his own). Moreover, in January 2013 a mandate for federal investigation of mass shootings authorized by President Obama changed the previous definition of what constitutes a “mass shooting” event by lowering the minimum number of victims from four to three, thereby increasing the number of such incidents so classified during President Obama’s second term.

Using Mother Jones‘ database of “US Mass Shootings, 1982-2016” shows that 31 mass shootings took place in the United States during the seven-year span from the start of President Obama’s first term through the end of 2015, four of which would not have been counted as such using previous standards. Of those 27 (not 162) mass shootings, eleven (not eighteen) involved the deaths of eight or more people.