Looking at both graphs together reveals that premium passengers in absolute numbers have increased from the year before recession (1998) til now with roughly 10%.
Doing a table-ish thing:
Premium: 2008 5.2M; 2009 4.1M = -20%; 2015 5.7M = +10% from -08, but c:a +40% from -09.
Economy: 2008 73M; 2009 71M = -2.5%; 2015 94M = +28.7% from -08, but c:a +32.4% from -09
Scrolling down on the IATA document to page 4 the traffic growth Mar -14 to Mar -15 was +4.4% in premium, +4.6% in economy, +4.6% in total
Still worried?