The details of retirement plans vary widely from company to company. A typical match is 3 percent of pay and requires the employee to contribute 6 percent to get that company money.

Facebook offered no company match in 2012 and 2013. Whole Foods provides an annual match of $152 based on a formula of 15.2 percent on the first $1,000 that workers contribute. That compares to more generous companies, such as the biotechnology company Amgen Inc., which contributes 5 percent of workers’ salaries whether they contribute or not. The company also will match as much as another 5 percent of employee salary deferrals.

Facebook says it will decide each year at its discretion whether to make a contribution. The company plans to provide a match later this year “as part of a comprehensive set of benefits,” said Facebook spokesman Tucker Bounds.

Whole Foods’ Ehrnstein said his company’s match was approved by 84 percent of its 80,000 employees.

Full Match

Kroger Co., the grocery store chain, is more generous than many companies. It matches 100 percent of the first 3 percent of workers’ salary deferrals, plus 50 percent of the next 2 percent of workers’ compensation. The company generally also pays an additional contribution of 1 percent to 2 percent based on tenure.

Kroger’s 401(k) match program is a way to attract and retain employees and is “a reflection of our company values,” said spokesman Keith Dailey.

Most employees have no idea how their company’s plan stacks up against competitors because the details are buried in opaque government filings. While companies file reports annually to the Labor Department that are available online, they’re difficult to access and the information provided isn’t consistent.

Corporate tinkering with 401(k) plans accelerated in the wake of the 2008 financial crisis. About 18 percent of 334 companies surveyed by consultant Towers Watson suspended or reduced contributions, a response to an urgent need to conserve cash. Yet when the liquidity crisis subsequently eased, about 23 percent of companies that reinstated company matches offered less generous contributions than before the recession.

Lower Match