Do you have a source for this information? I haven't seen a RAJAR figure for years, not since the editorial team stopped talking about them on the blog in 2016.
Before that, it went
Q1, 2011 - 5,010,000
Q2, 2011 - 5,080,000
Q3, 2011 - 4,980,000
Q4, 2011 - 4,920,000
Q1, 2012 - 4,750,000
Q2, 2012 - 4,630,000
Q3, 2012 - 4,850,000
Q4, 2012 - 4,870,000
Q1, 2013 - 5,080,000
Q2, 2013 - not found
Q3, 2013 - 4,820,000
Q4, 2013 - 5,000,000
Q1, 2014 - not found
Q2, 2014 - not found
Q3, 2014 - 4,700,000
Q4, 2014 - 4,740,000
Q1, 2015 - not found
Q2, 2015 - 4,620,000
Q3, 2015 - 4,760,000
Q4, 2015 - 4,840,000
Q1, 2016 - 4,700,000
Q2, 2016 - 4,950,000
Q3, 2016 - not found
though they frequently boasted that the figure had risen.