Genomic prediction of complex human traits (e.g., height, cognitive ability, bone density) and disease risks (e.g., breast cancer, diabetes, heart disease, atrial fibrillation) has advanced considerably in recent years. Using data from the UK Biobank, predictors have been constructed using penalized algorithms that favor sparsity: i.e., which use as few genetic variants as possible. We analyze the specific genetic variants (SNPs) utilized in these predictors, which can vary from dozens to as many as thirty thousand. We find that the fraction of SNPs in or near genic regions varies widely by phenotype. for the majority of disease conditions studied, a large amount of the variance is accounted for by Snps outside of coding regions. the state of these Snps cannot be determined from exomesequencing data. this suggests that exome data alone will miss much of the heritability for these traits-i.e., existing pRS cannot be computed from exome data alone. We also study the fraction of Snps and of variance that is in common between pairs of predictors. the DnA regions used in disease risk predictors so far constructed seem to be largely disjoint (with a few interesting exceptions), suggesting that individual genetic disease risks are largely uncorrelated. it seems possible in theory for an individual to be a low-risk outlier in all conditions simultaneously. Genomic prediction of complex traits and disease risks has advanced considerably thanks to the recent advent of large data sets and improved algorithms. These algorithms range from simple regression, applied to one SNP at a time to estimate statistical significance and effect size (e.g., as used in GWAS), to high dimensional optimization methods such as compressed sensing or sparse learning 1-4. They produce Polygenic Risk Scores (PRS) or Polygenic Scores (PGS): functions that map the state of an individual's DNA at specific locations (SNPs), to a risk score or predicted quantitative trait value. Predictors (PGS or PRS) now exist for a number of important traits and risks, many of which have undergone out-of-sample testing (i.e., validation in groups of individuals not used in training and from other data sets or from separate ancestries) 5-7. The genetic architectures (i.e., the properties of the SNPs activated in the predictors, which are sparse) uncovered vary significantly: the number of SNPs required to capture most of the predictor variance ranges from a few dozen to many thousands. In contrast, traditional Genome Wide Association studies (GWAS) can implicate the entire genome 8,9 , making them unwieldy to analyze. In the case of disease risk, the predictors are already good enough to identify genetic risk outliers. That is, individuals with unusually high (or low) genetic risk of a specific condition. There are many clinical applications for such predictors 5,10-19 (although there is still much work to be done to overcome sampling and algorithmic biases and disparity 20,21). Below we mention two possible future examples. Breast Cancer: Certain variants in the BR...