Did the HDI rankings change for many countries in 2018?

In general, the rankings change a little between two successive years because of the nature of the HDI component indicators. With the exception of gross national income per capita, other indicators change very slowly year to year.
Based on the consistent data series that were available on the cut-off date for downloading data for the computation of composite indices for the 2018HDR, there are several countries with ranks that changed between 2017 and 2018. The HDI values for 2017 and 2018 are given in Table 2 of the statistical annex. Table 2 also provides the change in ranks between 2013 and 2018.
The consistent data are based on the latest updates and data revisions and are obtained using the same methodology. The effect of change in achievements (improvement or decline) in human development indicators in terms of health, education and living standards is captured by comparing the HDIs obtained from such a consistent data series.
The difference between HDI values (and ranks) published in different editions of HDR represents a combined effect of data revision, change in methodology, and the real change in achievements in indicators. We advise users of the HDI not to compare the estimates from different editions of Reports, but to always use the consistent data given in Table 2 of the latest report or to use the data series available in the Internet database http://hdr.undp.org/en/data.