Across all industries, plans gained about $1 trillion in value, representing a 20 percent jump in plan assets over the previous year.

Actual participation rates continue to hover at around 81 percent, taking a breather after several years of increases led by widespread adoption of automatic enrollment options.

Total contributions from both employees and employers increased by about 8 percent year over year, although because the median contributions show a slight decline, the data mean more people than ever are participating, although their savings rate remains about the same.

The report ranked industry groups by average account balance, participation rate, rate of return, employee contributions, employer contributions, plan score and employee longevity.

The top 10 industries for retirement plans include industries you'd expect to do well. However, the report's insights into other industries might prove surprising, as might the performance metrics of a competitor's plan.

Financial advice and investment activities. This group is notable for its extremely high employee and employer contribution rates, which makes sense given that the average pay for someone in this space is likely to be substantially more than most other industry groups.

Because most employer dollars contributed to a plan are structured as matches to the employee contributions, there is a strong correlation between those two data points.

Certified Public Accountants. The average account balance across all CPA firms is $126,614, putting them about $3,000 ahead of lawyers and $5,000 ahead of financial advisors. It should also come as no surprise that these firms enjoy some of the longest- tenured employees, highest over-plan health scores and most contributions per participant.

Lawyers and legal services. Contributions and employee longevity combine to allow assets and average account balances to grow to a tremendous degree.

Average account balances begin at $116,000 among the smallest law firms and only go up from there, capping out at $272,363 among the large law firms of up to 5,000 employees. This represents the single highest dollar figure in the study.

Insurance providers and brokers. Providers and brokers have that great combination of good employee longevity and good employee and employer contributions. Those two items are the most important for achieving a successful retirement outcome, because they give the assets time to accumulate and grow.

Physicians. Physicians have an extremely high employee longevity score, ranking first with 13.5 years across the industry. This group ranks 12th in employee contributions,

Year over year, employee contributions were flat, and employer contributions actually saw a 5 percent decline, from $3,231 to $3,052.

Engineers. Already high rates of employee and employer contributions grew by about 2 percent and 3 percent, respectively, in the last plan year, and the 22 percent rate of return on plan investments helped account balances grow by more than $11,000.

Dentists. Dentists are both the most bottom-heavy and top-light group in the survey. The average account balance for micro-companies is $113,763, almost four times the $30,758 account balance for the largest companies in the space. Only doctors and lawyers have higher longevity rates than dentists.

Mining and utilities. Year over year, the mining and utilities group is similar to many of the other top-performing groups, with a 1 percent increase in employee contributions and a 2 percent increase in employer contributions.

Other financial and insurance activities. What these disparate firms have in common is a healthy rate of employee contributions and well-administered plans. Employee contributions increased by 7 percent, while employer contributions rose by 25 percent year over year.

Consultants. Individual performance metrics are all over the map, with very high rates of return and employee contributions counterbalanced by the lowest employee longevity score at only six years.