Accountable Care Organizations: Early Results and Future Challenges

A two-sided contract imposes stronger incentives on the ACO than a one-sided contract, which is both a strength and a weakness. While ACOs facing downside risk may respond earlier to the incentives, as some of the evidence thus far suggests, this risk may also propel ACOs to abandon this contracting model. In the Medicare Pioneer ACO program, for example, 9 of the 32 organizations exited the contract after year 1, which was allowed given the voluntary nature of participation. Seven organizations opted for the one-sided Medicare Shared Savings Program in year 2 and two left the ACO programs altogether. Downside risk was thought to be a principal concern for these organizations [40].Massachusetts providers in the AQC have thus far remained in the contract, but the AQC was a multi-year agreement to begin with.

Spillovers are another potential strength of the ACO model. Given that organizations care for patients across multiple payers, strong payment incentives in one payer population may affect care broadly. In the AQC, for example, recent evidence showed slowing of spending for Medicare beneficiaries associated with the contract in similar settings and categories of care as for the Blue Cross Blue Shield patients [41].

Weaknesses of the ACO Model

Still in its nascent stages, the ACO paradigm faces a number of challenges. Some relate to inherent weaknesses of the model, while others relate to the institutions and economics of the broader health care economy. At a contractual level, a key challenge is setting the target growth rate of the budget. If too low, providers may be overly constrained; if too high, providers may not have enough incentive to change practice. In an extreme case, if the target is set above what spending would have been under the old arrangement, an ACO contract can in fact be cost increasing on claims spending alone. Financial rewards such as shared savings and quality bonuses can help offset the risk, but they also make it more difficult for the ACO contract to generate net savings.

Achieving the right balance of risks and rewards is difficult. As noted above, a one-sided contract may not be strong enough to induce behavior change [42,43],but a two-sided contract may be too risky, driving providers who are unable to align incentives and coordinate care to exit the model [44].Although the percentage of shared risk borne by payer versus provider can be negotiated, putting financial risk on providers in a palatable way will be a key challenge. Financial risk can be more daunting if ACOs do not know in advance which patients they are responsible for, as in contracts with retrospective attribution rules and enrollees in unmanaged plans. A payer can help providers handle risk by sharing data on spending and identifying potential areas of overuse and low value care. Payers can help further by implementing risk corridors, providing reinsurance, or improving risk adjustment of the organization’s global budget. But with all that said, it remains to be seen whether providers around the country will be willing to bear substantive risk.