A buyback announcement means nothing on its own. What matters is whether weighted-average-shares actually fall. Many companies repurchase heavily and still dilute owners, because grants exceed repurchases.
Compute the annual change in diluted shares and set it against repurchase spending. That comparison, not the announced authorisation, is the honest measure of capital returned per share.
Example: Northwind Tools spends $40M on buybacks yet diluted shares rise from 93.8 million to 96.0 million, up 2.4%, because $32M of stock grants more than offset the repurchases.
Related: weighted-average-shares, sbc-as-percent-of-revenue, capital-allocation, basic-versus-diluted-eps, eps