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Data for this report was collected from other sources and forms of documentation as early as the day of the event. Information and details such as population sizes, weather conditions that day, human population distribution and more were all information collected from that day of the event. Other forms of data collected, ranging over the time of the event occurring to the publication time, include factors such as the quality of the air, water, animals and living conditions surrounding the plant. Human radiation levels and infection were also gathered, radiation levels of crops and much, much more were all statistics and data collected over roughly twenty year timespan that this report covers. This is actually one of the main driving points of the report, listed in the title "twenty years of experience." It compiles 20 years of research and findings into one large report.

After the Fukushima disaster, thyroid examinations were performed on residents less than 18 years of age. The first three years post disaster are noted as the "Initial phase" and act as a control. Of those tested, 113 cases were suspected of or found to have thyroid malignancies, 99 of those underwent surgery. After this, the goal became to compare and observe prevalence of thyroid cancer in this initial screen program with historical controls based off if there was a nuclear disaster or not.

For this study, the observed/expected ratio was calculated for residents less than 20 years old. Observed prevalence of cancer was calculated using numbers found in the initial thyroid screening program mentioned above. Expected prevalence was then calculated by using a life-table method utilizing national estimates of thyroid cancer incidences before the disaster. The population of Fukushima was taken into account.  A 5 year cumulative risk of thyroid cancer incidences was calculated for the year of 2010.  This 5 year risk was then converted to a 1 year cumulative risk using a method called spline smoothing. Then the age-specific prevalence of thyroid cancer was estimated by multiplying the 0 year old population by the age specific risk in 2010. 

I have done research involving cancer rates and their correlation with power plants (in my case Indian Point.) Doing that research caused me to read hundreds of studies similar to this one where estimates are made using calculations based off cancer rates before the incident and then taking them and putting them into context of a post disaster area. I wouldn't quite say that this method is new or inventive but it follows similar methodology to other studies of this same caliber, yet there are aspects that make it more unique such as converting the 5 year to 1 year cumulative risk using a spline smoothing method.