Note 15 — COMMON SHARE DATA
Weighted-average shares used in computing net income per share are as follows: 
(In millions)
 
2016
 
2015
 
2014
Weighted-average shares — basic:
 
83.9

 
87.8

 
92.3

Plus dilutive impact of share-based compensation
 
0.7

 
0.9

 
1.2

Weighted-average shares — diluted:
 
84.6

 
88.7

 
93.5


Outstanding share-based awards with exercise prices greater than the average price of the common shares are anti-dilutive and are not included in the computation of diluted net income per share. The number of anti-dilutive options and awards was 0.2 million and 0.4 million at December 31, 2016 and 2014, respectively. Less than 0.1 million options and awards were anti-dilutive for the computation of diluted earnings per common share at December 31, 2015.
We purchased 3.0 million, 4.5 million and 6.3 million shares in 2016, 2015 and 2014, respectively, at an aggregate cost of $86.2 million, $156.1 million and $233.2 million, respectively.

About Earnings Per Share Disclosures

The earnings per share disclosure breaks down the calculation from net income to both basic and diluted EPS, revealing the full impact of a company's capital structure on per-share economics. The reconciliation between basic and diluted share counts exposes how many stock options, RSUs, convertible securities, and warrants are potentially dilutive to existing shareholders.

Key signals: a widening gap between basic and diluted shares indicates growing dilution from equity compensation or convertible instruments. Anti-dilutive securities excluded from the diluted calculation deserve attention — they represent latent dilution that will materialize if the stock price rises. Watch for the effect of share buybacks on per-share metrics: EPS growth driven primarily by repurchases rather than income growth signals weakening fundamentals. Compare year-over-year changes in the diluted share count against equity compensation expense to assess whether management is effectively managing dilution.