Some things work; some things don’t. This is hardly news. Yet if you read reports from charities, foundations, and corporate sustainability departments, you’d think that success was guaranteed—virtually every single thing allegedly worked brilliantly. “So flattering it’s laughable,” commented one funder recently on reports by charities working in criminal justice in the UK.

So hats off to the C&A Foundation—attached to the well-known C&A retailer—which works to improve the lives of workers in the apparel industry. This month, the foundation published a full and honest account of a program it ran with suppliers—some parts of which worked well and some parts of which didn’t. It thereby joins a growing but still tiny group of nonprofits that appraise their own work in public.

Created in 2011—long before the horrific factory disasters in Bangladesh in 2012 and 2013 re-highlighted problems with garment workers’ rights and conditions—C&A Foundation created a Sustainable Supplier Program (SSP) in garment factories that supply C&A and other retailers. The goal was to improve working conditions (such as pay and hours) and productivity in factories, and generate a virtuous circle between the two. It ran for two years, in 18 factories in five countries across Asia, and covered 22,000 workers.

Speaking broadly, the SSP worked. Sewing efficiency, an important measure of productivity, improved by 20 percent across all factories, and take-home wages excluding overtime, an important measure of worker conditions, increased by 15 percent. Furthermore, worker turnover dropped by 24 percent, and each factory saved an estimated €450,000 (about $356,000).

C&A Foundation’s new report is true to its title, “Frankly Speaking,” in telling the other side of the story too. For example, it gives factory-level data on changes in sewing efficiency, revealing that although some factories saw sewing efficiency rise by 60 percent, elsewhere it got about 15 percent worse. Similarly, overtime (a major driver of worker dissatisfaction and hence staff turnover) almost disappeared in some places, yet rose markedly in two factories and, weirdly, more than tripled in one factory.

As well as sharing the raw data, “Frankly Speaking” discusses some of what the team did wrong: The stories are lightly veiled as “challenges” and “things we’d do differently next time,” but nonetheless, such candor is rare in foundation publications.

The report discusses how 18 factories is too many for a tightly managed pilot and yet too few to give statistically robust results. So the program wasn’t really a pilot but neither was it a proper test. Those 18 factories were spread across five countries and were supported by one of two “implementers,” so it’s impossible to figure out whether changes in performance were due to the program, the implementer, the country’s economic conditions, or other factors. Equally, the foundation didn’t adequately involve C&A buyers and didn’t link factories’ participation in the program to orders (understandably, factories’ primarily concern is sales, so recruiting factories into the program was tough). A third lesson is that the foundation asked factories to contribute to the cost of the program and required their full contribution up-front. In hindsight, perhaps the program could have staggered payments so as to come from productivity improvements if and when they occurred. Fourth, the foundation didn’t collect data on costs and savings as the program went along, so instead built a financial model afterward to estimate the savings, which clearly isn’t as reliable. And so on.

What’s most striking about these “challenges” is just how normal they are. So human. Every single nonprofit and social entrepreneur has made similar mistakes and seen others do so too. Surely it’s a bit ridiculous that more of us don’t acknowledge them, and instead pretend that everything works just great.

It’s also dangerous. Clearly it’s hard for donors or operating organizations to make evidence-based decisions if much of the evidence is missing. The effect of not speaking publicly about things that don’t work is that the evidence is skewed; it becomes unreliable. Given that in the social sector we are all (notionally!) on the same side, it’s surely in our own interest to share these lessons.

C&A Foundation’s main motive for publishing this report is to enable the industry to learn together, and hence faster. As the Bangladesh incidents showed, the stakes are high. The clothing industry is under intense and sustained pressure to reduce prices, but as the foundation’s executive director Leslie Johnston says, “Competition shouldn’t be at the cost of workers’ well-being.” Though many brands run programs to improve conditions in their supplier factories—and in fact, since most factories supply several brands, many factories have several such programs running concurrently—there’s little discussion about what they are achieving or learning. C&A Foundation is pushing for more collaboration within the garment industry and for more openness.

This effort echoes the Shell Foundation’s rationale for the unusually honest self-assessment it published in 2010 as its first decade of work drew to a close. Shell Foundation said that the experience of identifying major lessons, and acknowledging and publishing them was helpful internally. Despite the fact that other organizations rarely emulate this openness, the report is often cited—not least for showing that transparency isn’t fatal and that collecting hard comparative data is possible.

Johnston hopes that “Frankly Speaking” will move her industry forward, just as more openness could do in many areas of philanthropy and social innovation. She says, “We suspect that our work to improve conditions could be more rapid if we knew what others were learning. We’re sharing our results so that everybody can improve faster.”