The exact number of variants is disputed, but the more texts there are, the more likely there will be variants of some kind. Variants are not evenly distributed throughout any set of texts. Charting the variants in the New Testament shows it is 62.9 percent variant-free. The impact of variants on the reliability of a single text is usually tested by comparing it to a manuscript whose reliability has been long established. Though many new early manuscripts have been discovered since 1881, there are critical editions of the Greek New Testament, such as NA28 and UBS5, that "have gone virtually unchanged" from these discoveries. "It also means that the fourth century "best texts", the 'Alexandrian' codices Vaticanus and Sinaiticus, have roots extending throughout the entire third century and even into the second".