Concurring with the comments on the Skeptics question, I am also not aware of a standardized operationalization of "number of decisions" that could be used to produce a meaningful measure for this, and to my knowledge no (serious) research has attempted to calculate a daily tally.
This clearly poses little challenge for the numerous references to this and other unsourced/uncited statistics. While references on various blogs, social media, self-help books, and other questionable sources are not of much note, there are a few citations made on media outlets that readers might take more seriously, such as:
The Telegraph UK (2016):
They say the average person makes 35,000 decisions a day.
Huffington Post UK (2014):
According to newspaper ‘USA Today’ the average adult makes about
35,000 decisions each day.
Phrasings such as "they say...", "it is thought that...", "according to various online sources...", etc are not very committal about validity, and the above quotes do only appear in the "Lifestyle" sections of these newspapers, so there is not much impetus for journalistic integrity.
Articles often mention other corroborating research to make the "35,000" statistic sound more plausible. An example from a different Huffington Post UK (2011) article (found on Mirror magazine as well):
The average Brit makes 773,618 decisions in a lifetime but lives to
regret as many as 143,262 of them, a study has found. ... The study of
2,000 indecisive Brits, by Nintendo Puzzler Mind Gym 3D, found that
That's right, Nintendo - the game system company - purportedly conducted this apparently unpublished poll, giving a much lower number of decisions statistic (around 27 per day).
Another example on a Psychology Today (2012) article:
According to a survey by Columbia University decision researcher,
Sheena Iyengar, the average American makes approximately 70 conscious
decisions every day.
Sheena Iyengar, a professor of business at Columbia, also apparently did not publish her survey findings, but she does discuss it on TED (2012):
I recently did a survey with over 2,000 Americans, and the average
number of choices that the typical American reports making is about 70
in a typical day.
Here is something from reference.com:
Each individual is different, so it is impossible to pinpoint a
specific number of daily decisions that applies to every individual,
but Time magazine puts the number in the thousands.
The referenced Time Magazine article indeed says:
Every day, we face thousands of decisions both major and minor ...
How silly. Here is another interesting item from reference.com:
The average person has about 48.6 thoughts per minute, according to
the Laboratory of Neuro Imaging at the University of Southern
California. That adds up to a total of 70,000 thoughts per day.
The source cited for this amazing claim does not corroborate this ... any more, but it did!
How many thoughts does the average person have per day?
So let's see, 70k thoughts per day, 35k decisions per day ... that's about 1 out of every 2 thoughts is a decision? The other 1 in 2 thoughts must be the ones about sex. But wait, what's the asterisk (*) about? Ah:
*This is still an open question (how many thoughts does the average human brain processes in 1 day). LONI faculty have done some very
preliminary studies using undergraduate student volunteers and have
estimated that one may expect around 60-70K thoughts per day. These
results are not peer-reviewed/published. There is no generally
accepted definition of what "thought" is or how it is created. In our
study, we had assumed that a "thought" is a sporadic single-idea
cognitive concept resulting from the act of thinking, or produced by
spontaneous systems-level cognitive brain activations.
The most credible corroborating research I've seen so far is the Wansink & Sobal (2007) paper: "Mindless Eating: The 200 Daily Food Decisions We Overlook", published in the journal Environment and Behavior. Keeping in mind that neither author is a cognitive scientist, and that this article concerns nutritional health, not psychological measurements, and that the lead author has faced dozens of retractions and corrections of his published papers, and was barred from research due to scientific misconduct, this is nonetheless a very well cited paper. In the paper, the authors explain:
One hundred and fifty adults ... were initially asked to estimate how
many total decisions about foods and beverages they make in one day.
They were then asked six questions about snacks, six questions about
meals, and six questions about beverages. ... While the typical person
estimated they made around 15 food and beverage decisions in a day,
the average that was calculated from subsequent questioning was 219,
approximately 200 more.
I'm not sure if the authors truly believe that this method conclusively sets the total number of daily food-related decisions, or if they were just pointing out that we are often not aware of many of the decisions that we make, but it is not difficult to imagine that if the survey contained more or fewer detailed "subsequent" questioning, then the total number of decisions would increase or decrease accordingly. Regardless, this paper is an important reference for the author's self-help book - Mindless Eating (2006):
The phrase "mindless eating" refers to the empirical finding that
people make nearly 20 times more daily decisions about food than they
are aware of (an average of around 200 each day).
With a range of between 27 and 35,000 decisions per day, I think you can just pick any number you want for this statistic. These types of claims are often associated with reference to research on decision fatigue and ego-depletion - a largely discredited idea about the limits of human capacity for decision making.
Anyways, I hope you had as much fun reading this answer as I had writing it. Also, according to the Arnon Science Foundation, recent research proves that voting up this answer will make your day up to 32% better, so be sure to improve your average daily decision making by showing your support!