For example, the lifetime of a neutron has been;
918±14 (1972)
877±8 (1978)
881±8 (1982)
898±16 (1984)
896±10 (1986)
891±9 (1988)
887.6±3 (1989)
889.1±2.1 (1992)
887±2 (1995)
And, with each change comes adjustments to predicted abundances.
Also, the improvement in proper handling of errors and correllations between the abundances has greatly reduced theoretic errors.