Clifford is senior research fellow in health economics at Australian Centre for Health Service Innovation (AusHSI) at QUT and Jamieson Trauma Institute at RBWH. He has expertise in economic evaluation of healthcare interventions, health econometrics, big data analytics, large cohort data linkage and burden of disease studies. His current research focuses on the economics of trauma. Specifically, he works on the economic cost of transport and work-related injuries, burden of injuries, and environmental and economic drivers of injuries using linked administrative health and insurance claims data.

Clifford also has interest in development economics, especially topics on household welfare and human capital. His works have been published in prestigious medical journals such as Lancet Healthy Longevity, European Heart Journal, Age and Ageing, International Journal of Cardiology as well as highly ranked economics journals such as Health Economics, Energy Economics, World Development, Applied Economics, and European Journal of Health Economics.