I have read or heard much about the dilemma of NIH applicants as they struggle to understand their chances of receiving NIH funding. As budgets flatten and tighten, this discussion has heated up. To declare that NIH success rates have hovered around 20% for the past five years does little to calm the storm of concern when we hear about shrinking percentiles and paylines. So how is it possible to have a success rate of 20% but a payline at the 7th percentile? Let’s take a few moments to sort out what these things mean and think about how these numbers are derived and how they can differ.
It all starts with the impact. This score is assigned by reviewers to indicate the scientific and technical merit of an application. Impact scores range between 1 and 9. A score of “1” indicates an exceptionally strong application and “9” indicates an application with substantial weakness. (I always wondered why at NIH low = good and high = bad but that predates me!) In assigning an impact score, reviewers consider each of five scored criteria: significance, investigator, innovation, approach, and environment, along with other factors like protection of human subjects and vertebrate animal care and welfare. Read more about scoring.
The percentile rank is based on a ranking of the impact scores assigned by a peer review committee. The percentile rank is normally calculated by ordering the impact score of a particular application against the impact scores of all applications reviewed in the current and the preceding two review rounds. An application that was ranked in the 5th percentile is considered more meritorious than 95% of the applications reviewed by that committee. This kind of ranking permits comparison across committees that may have different scoring behaviors. It is important to note than not all research project grant applications (RPGs) are percentiled. For example, applications submitted in response to a request for applications (RFA) are usually not percentiled. In the absence of a percentile rank, the impact score is used as a direct indicator of the review committee’s assessment. Read more about percentiles.
Many NIH institutes calculate a percentile rank up to which nearly all R01 applications can be funded. For grant applications that do not receive percentile ranks, the payline may be expressed as an impact score. Institutes that choose to publish paylines in advance (see an example) calculate the payline based on expectations about the availability of funds, application loads, and the average cost of RPGs during the current fiscal year. Other institutes prefer to describe the process for selecting applications for funding (see an example) and then report on the number of applications funded within different percentile ranges at the end of the fiscal year (see an example). Because the NIH is currently operating on a continuing resolution and funding levels for the remainder of this fiscal year are uncertain, most of the NIH institutes have offered less detail this year than in the past.
But remember, even when an IC establishes a payline, applications outside of the payline can be paid under justified circumstances if these applications are a high priority for the particular institute or center. When these select-pay/out-of-order/priority pay/high priority relevance selections are made, it may result that other applications within in the payline are not paid because funds are no longer available to support them.
The success rate calculation is always carried out after the close of the fiscal year, and it is based on the number of applications funded divided by the number of applications reviewed and expressed as a percent. To better reflect the funding of unique research applications, the number of applications is adjusted by removing revisions and correcting for projects where the resubmission (A1) is submitted in the same year as the original application (A0). Read more about success rates.
Now we are equipped to answer our earlier question. How is it possible to have a success rate of 20% but a payline at the 7th percentile? There are several real-life reasons why paylines (the ones that use percentiles) can be either higher or lower than success rates.
- Applications that are not percentiled are still factored into the success rate calculation. Thus, funding a number of awards that are not assigned percentiles will increase the success rate without changing the payline.
- The success rate for a particular fiscal year is a reflection of the funded applications and can include applications reviewed in the previous fiscal year; whereas, the payline encompasses only applications reviewed in that fiscal year. So awarding applications that were reviewed in the previous year will also increase the success rate.
- The average quality of the applications assigned to an institute will also affect its payline. If an institute happens to receive a set of applications with very good (low) percentile scores, its success rate will be higher than its payline, all else being equal. For example, in fiscal year 2010, the NIGMS R01 success rate was about 27% but the midpoint of the funding curve occurred close to the 21st percentile.
Whew, you made it through. The difference between paylines, percentiles and success rates remains a confusing topic because of the compounding factors that rule out a simple linear relationship. You need to consider all the factors when assessing the potential for an individual application to be funded. Your best advisor on this issue, because of the differences in the ICs and programs, is your NIH program official. Give him or her call.