Betting on the 20: Jack Valero’s Unfiltered Sample Size
Jack Valero’s book, El Opus Dei Sin Filtros, promises an authentic, "unfiltered" look at Opus Dei by sharing the stories of 20 current members. (The above image shows 1 of 6 posts made by him
on his Facebook account on under 48 hours, yep this is a grown up man who is over 70 years of age)z
While personal stories offer valuable insight, putting 20 active members forward as a definitive representation of the organization runs into major statistical issues.
The Baseline Attrition Problem
If we treat these 20 featured members as an uncurated cohort and track them over time, historical trends suggest a significant percentage will not remain:
Celibate Members (Numeraries & Associates): Attrition rates prior to permanent incorporation (Fidelity) sit between 50% and 80%. Post-fidelity they sit between 30-40%. Statistically, several young celibate members in a random sample of 20 would likely depart over time. OD does not give the official numbers for some reason even though you would think the truth and transparency here matters, likely to do with the fact that the concept of ‘belonging’ to the prelature by lay members is actually a highly contest matter inside the church.
Supernumeraries (Married Members): Dropouts among married members are lower, but long-term departure rates still sit around 30% to 50%.
The Sampling Bias: Two Scenario Outcomes
From a basic research perspective, Jack’s group of 20 leads to one of two logical conclusions:
Option A (Survivor Bias): The 20 individuals were chosen at random from current members. If so, basic probability indicates that over the next few decades, several of them will leave the
organization, making the book a snapshot of a moving target.Option B (Selective Sampling): Jack did not choose these 20 people at random. Instead, he selected a specific subgroup of highly committed, zealous, or long-standing members who are statistically far more likely to stay.
The Verdict
Whether through survivor bias (ignoring the thousands who have already walked out the door) or selective sampling (hand-picking the most committed members to minimize future exits), a sample of 20 active members cannot serve as a valid control group.
To get a truly unfiltered picture of any institution, a study must measure both sides of the ledger: the people who stay, the subgroup selected to represent them, and the vast numbers who choose to leave.