Related: See all DOL fiduciary rule coverage here

The ratings agency projected the cost of implementing the rule will be $2.4 billion, more than twice what the DOL and industry had been estimating.

Morningstar said between $250 billion and $600 billion of low-account balance IRAs will flow out of commission-based accounts as a result of the rule, and more than $1 trillion of retirement assets would flow into passively managed investment funds upon the rule’s implementation.

2. Vanguard separates from pack

The New Year brought totals for 2015 fund flows, which showed Vanguard had an industry record of $236 in retirement assets flow into its mutual funds. More than $33 billion flowed into Vanguard target date funds.

3. Even low-cost Vanguard funds too costly for 401(k) plans

Participants sued fiduciaries of health care giant Anthem’s 401(k) plan.

The suit claimed, in part, that its investment lineup, which was dominated by retail-class shares of Vanguard funds, constituted a breach under the Employee Retirement Income Security Act.

Related: Anthem participants in 401(k) suit face uphill battle

Attorneys at Schlichter, Bogard & Denton alleged retail shares were offered when institutional shares were available. In the case of one fixed-income fund, the spread between the two share classes was two basis points.

The case marked an aggressive turn in the strategy of the plaintiffs’ bar. Now, even plans featuring low-cost Vanguard funds were fair game. ERISA experts said participants in the case against Anthem had an uphill battle. Vanguard was not named as a defendant in the suit.

4. Republicans introduce alt legislation to DOL rule

In February, Republicans on the House of Representatives Education and Workforce Committee pass two bills as alternatives to DOL’s fiduciary rule on a party-line vote. The bills would never see a full vote on the House floor.

Related: Laws requiring Congress's approval of DOL fiduciary rule move to House

The bills did have Democratic co-sponsors. Late in February, Rep. Jared Polis, requested the Labor Department give members of Congress a look a the changes in the finalized version of the rule before it is released.

Polis and other Democrats continued to voice concerns over the rule’s potential impact on small investors. But by summer any evidence of Democratic opposition to the rule would be silenced.

5. Speaker Ryan weighs in on fiduciary rule

In March, House Speaker Paul Ryan, R-WI, goes on the record against fiduciary rule, weeks after a report out of Senate claims to prove that the DOL did not adequately coordinate with the Securities and Exchange Commission in promulgating the rule.

Related: Obama, Ryan circle the wagons as OMB finalizes fiduciary rule

SEC Chair Mary Jo White would tell Congress later in month that the SEC did in fact coordinate with DOL throughout the rulemaking process.

6. DOL releases finalized fiduciary rule

On April 6, the final fiduciary rule is released, some six years in the making.

Considerable changes were made to the proposed version of the rule.

“At its core, this rule ensures retirement savers get investment advice in their best interest,” said Labor Secretary Thomas Perez in a press call. “If that sounds like it is obviously the right thing to do, that’s because it is.”

Republicans immediately vow to fight the rule’s implementation. Democrats vow to defend it.

7. Not a legal leg to stand on

In the weeks after the rule is released, Rep. Ann Wagner, R-MO, reintroduces legislation that would stop the fiduciary rule by requiring the SEC to issue a fiduciary rule first.

Also, rumors abound of legal challenges to the rule. In a press conference, Sec. Perez says opponents of the rule won’t “have a legal leg to stand on in a lawsuit.”

8. Treasury denies relief plan for Teamsters pension

The Treasury Department denies a request by the Teamsters Central States pension plan to reduce benefits to retirees in an effort to extend the solvency of the plan, which is projected to run out of assets within 10 years.

The Central States plan was the first to apply for the right to claw back pensions under the 2014 Multiemployer Pension Reform Act.

9. Obama vetoes bill to block fiduciary rule

At the end of May, the Senate passes legislation that originated in the House to block the fiduciary rule. President Obama promptly vetoes it.

10. First lawsuit against rule emerges

The U.S. Chamber of Commerce files the first of several lawsuits against the fiduciary rule in a Texas federal court. Suits would follow in the District of Columbia, Kansas and Minnesota.

11. Brexit Vote proves unreliability of prognosticators, pollsters

In June, Britons voted to leave the European Union, sending financial markets reeling—they soon recovered—and putting a serious hurt on the reputation of pollsters here and across the pond. The outcome of the referendum was widely predicted to be in favor of staying in the EU.

12. Lawsuit against small 401(k) withdrawn

In July, a lawsuit against a $9 million 401(k) plan was voluntarily withdrawn in a Minneapolis federal court. The case was viewed by many as an ominous warning for small sponsors of 401(k) plans.

13. Safe Harbor released for state-run plans

At the end of August, the DOL released its safe harbor for state-run retirement plans, which would be extended to qualifying municipalities and counties in December.

California, Illinois, Maryland and Connecticut have already passed legislation that will mandate automatic enrollment in state-administered retirement plans for businesses that offer a savings option.

14. DOL survives first challenge

A federal judge in the U.S. District Court for the District of Columbia rules against the National Association of Fixed Annuities. The decision was expected. NAFA is appealing in the D.C. Court of Appeals.

15. Trump wins

Donald J. Trump is unexpectedly elected President of the United States. Speculation of the fiduciary rule’s impending doom immediately emerges.

16. DOL survives second suit in Kansas

Market Synergies, a Topeka-based independent marketing organization, losses its lawsuit in a Kansas federal court against the DOL rule. ERISA experts had expected a victory for industry in the Kansas court. The IMO has not yet said if it will appeal the case.

17. Waiting it out in Texas court

Arguments in the consolidated lawsuit against the DOL are heard in the Northern District of Texas. A decision has yet to be released, though it could come by the end of the year.

18. Miners snubbed in continuing resolution

Despite a considerable fight from Senate Democrats, the Miners Protection Act is not passed with the continuing resolution that funds the government through next April.

A group of Senators form coal states threated to force a government shut down if the health care and retirement benefits of 120,00 coal miners were not secured in the temporary budgets. Temporary funding was budgeted. Senate Democrats have vowed to address the Miners Protection Act early in the next Congressional session.

19. Trump names Labor Secretary

President-elect Trump names Andrew Puzder, CEO of CKE Restaurants, to head the Labor Department.

Related: Fast-food CEO Puzder nominated

The transition team remains silent on its intent with the DOL rule, but speculation within industry is projecting the rule’s April 10, 2017 implementation date may be delayed.