There are various hypotheses on the relative importance of the individual soil-forming factors of Jenny's (1941) functional-factorial approach. The quantitative influence of each soil-forming factor on the expression and rates of soil-forming processes, and in particular the influence of the different factors in combination, have not yet been fully explored. The aim of this study was thus to quantify the influence of the soil-forming factors on the rates of podzolization, using data from 48 studies of soil chronosequences developed in sandy parent materials, located in the humid mid and high latitudes. These studies contained altogether 259 soil profiles of known age, for which we tested existing hypotheses on the influence of different soil-forming factors. The formation of an E horizon and its increase in thickness over time is one of the characteristic features of Podzol formation. As it is one of the few features that was described in all 48 studies, we used it as an indicator of progressive podzolization. Through statistical analysis, we investigated how E horizon thickness is affected by latitude, longitude, mean annual precipitation, mean annual temperature, range between minimum and maximum monthly temperature, annual number of days with frost, vegetation class, sand content, clay content, and soil age. Because E horizon thickness exhibited a zero-inflated (semi-)continuous distribution, we opted for a zero-altered gamma (ZAG) model, consisting of a Bernoulli and a Gamma part. The Bernoulli part shows how the probability of the presence of an E horizon changes with soil age and environmental conditions. The Gamma part of the ZAG model allows for capturing the effects of the covariates on E horizon thickness. Our results indicate that vegetation is the most important factor for both (1) the age at which podzolization starts (used indicator: first occurrence of an E horizon), and (2) the rate of podzolization thereafter (used measure: increase of E horizon thickness with soil age). Climatic factors such as mean annual precipitation and range of temperature play subordinate roles. They can be important in determining the time to initiation of podzolization, but are less important for the rates of podzolization. Within this set of sandy soils, we did not identify a significant influence of sand content, neither on the start nor the rates of podzolization.