It should be no surprise that the largest defined contribution plans are sponsored by companies that have been well-recognized brands for decades. They’re big in part because their participants have been feeding dollars into the plan for so long.

“The amount of time a plan has been around has a direct relationship with how much money is in it,” said Eric Ryles, managing director of Judy Diamond Associates, a provider of data and analytics tools for retirement advisors and plan sponsors.

A recently reported analysis by Judy Diamond, which is owned by the same parent company as LifeHealthPro, showed that the top 1 percent of 401(k) plans, or top 5,400 plans, hold $3.06 trillion, or 71 percent, of all plan assets in the country. 

So, who’s on that list? Where are all those dollars? What follows is a closer look at 10 biggest 401(k)s, based on asset data as of Dec. 31, 2014.

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10. JP Morgan Chase

Total assets: $20.45 billion
Total participants: 290,183
One-year rate of return: 20.5 percent
Accounting firm: Meaden & Moore Ltd. 

The New York City-based investment bank is one of two financial firms in the top 10. 

9. Wal-Mart 

Total assets: $20.65 billion
Total participants: 1.167 million
One-year rate of return: 12.64 percent
Accounting firm: Ernst & Young 

No company comes close to the size of Wal-Mart in terms of the number of people it employs in the U.S. or around the world. Of the 2.2 million employed at the retailer globally, more than half are enrolled in a company 401(k) plan. 

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8. United Technologies 

Total assets: $20.83 billion
Total participants: 96,448
One-year rate of return: 19.21 percent
Accounting firm: Pricewaterhouse Coopers 

The Hartford Connecticut-based manufacturer of aircraft and industrial technologies employs about 218,000 people globally, and is joined by competitors Boeing and Lockheed Martin in the top 10 largest 401(k) plans by assets. 

7. Exxon Mobil 

Total assets: $23.88 billion
Total participants: 44,023
One-year rate of return: 18.28 percent
Accounting firm: Pricewaterhouse Coopers 

When it comes to its 401(k) plan, the world’s largest oil producer punches way above its weight-class — the 44,023 participants in its plan is substantially lower than any other top 10 firm. 

Image: (AP Photo/Gene J. Puskar)

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6. Lockheed Martin 

Total assets: $27.15 billion
Total participants: 124,429
One-year rate of return: 24.26 percent
Accounting firm: Mitchell & Titus LLP 

Last December, the Bethesda, Maryland-based defense contractor agreed to settle a nine-year old claim alleging $1.3 billion in damages to participants in its 401(k) plan. Terms have the settlement have yet to be disclosed. 

5. General Electric 

Total assets: $27.45 billion
Total participants: 242,674
One-year rate of return: 26.92 percent
Accounting firm: KPMG LLP 

GE had the highest one-year rate of return on its plan in 2013, the latest year for which data is available. That was a bit better than the Dow Jones Industrial Average’s 26.5 percent return for 2013. 

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4. AT&T

Total assets: $29.82 billion
Total participants: 242,409
One-year rate of return: 14.41 percent
Accounting firm: Ernst & Young 

The Dallas-based communication giant automatically enrolls eligible employees and defers 3 percent of salary, with a company match of 80 percent of a participant’s “basic contribution.” 

3. Wells Fargo 

Total assets: $33.03 billion
Total participants: 358,881
One-year rate of return: 22.2 percent
Accounting firm: KPMG LLP 

The San Francisco-based bank matches contributions dollar for dollar up to 6 percent of eligible pay on a quarterly basis, after one year of service.

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2. Boeing 

Total assets: $45.12 billion
Total participants: 227,541
One-year rate of return: 21.15 percent
Accounting firm: Deloitte & Touche LLP 

Last year, the Seattle-based aerospace company announced it was freezing its defined benefit pension plan, and moving 68,000 non-union employees into its 401(k) plan. 

1. IBM

Total assets: $48.15 billion
Total participants: 200,504
One-year rate of return: 12.74 percent
Accounting firm: Pricewaterhouse Coopers 

The biggest 401(k) plan would also seem to be the most conservatively allocated. Of the top 10, it had the lowest rate of return on its plan in 2013, 12.74 percent. That’s less than half the return on GE’s plan, the best performing of the top 10.