The robust measurement of quality in healthcare is a pre-requisite for monitoring health system performance and is key in driving health system improvements. Despite the rise in process and outcome indicators, little agreement exists amongst health experts regarding the suitability of a single metric to measure quality in healthcare across multiple dimensions, such as safety, effectiveness and efficiency. However, over the past decade, hospital emergency readmission rates have developed into a prominent marker of healthcare quality, with an enhanced policy focus on reducing readmission to improve quality. Particularly, in England following the 2010 government white paper Equity and Excellence: Liberating the NHS, several policies were introduced, including financial penalties for hospitals with excess readmission rates, or funding transfers to social care services to reduce future hospital readmissions. Despite this effort to reduce readmission rates, little is known in the literature about the impact of this enhanced policy focus in England and thus, in this thesis, I examine the dynamics in quality of care based on changes in readmission rates. Following a review of the literature on the methodological consideration when using readmission rates as a measure for healthcare quality, I assess trends and variation in readmission rates across NHS Trusts between 2006 and 2016. Next, I validate the readmission metric against patient-reported outcome measures in hip and knee replacement patients in chapter 4. The final two substantive chapters present an impact evaluation of two English health policies on quality of care, one national-level payment reform (i.e. financial penalties for hospitals with excess readmission rates), and one area-level health system reorganisation (i.e. centralisation of stroke care in London).