You need to know the finances of your own company. And need to know the economics of your chosen space. Cold.
To grow, you need to design for growth. And communicate your business objectives with crystal clarity. To speak intelligently and forthrightly requires you to master the language of entrepreneurship. It begins with your peer network. Reach out to other founders, even competitors. Go to events. Don't be afraid to cold email. Ask direct questions relating to everything and research every concept you don't know.
Also begin a steady diet of news: Economist, Bloomberg, FT, WSJ, Reformed Broker. Treat it like you would an essential component of your startup's "culture". Because you may think the fact that 10Y US Treasury yields are holding above 2.40% doesn't directly effect your company. But it does.
The advantage to begin mastery of econ in your 20s, is that a decade later when you hit 30 and need to make long term decisions out of necessity, it will no longer be guesswork. You'll know mathematically what your risk appetite is. And know on an instinctual level, what separates a good investment from the pack.
As for the social science side, there is no better place to start than the "Neuroeconomics" work of this year's Nobel Laureate Richard Thaler. Start on "Nudge" and "Misbehaving". True game-changers. And then onto Daniel Kahneman's "Thinking Fast and Slow".
And do give credence to the classic that kicked it all off: Adam Smith and "The Wealth of Nations". As important as Descartes, Kant, Locke, Rousseau and Jefferson to our modern world.
Best of luck, dprophecyguy!
Then, you look outside the windows and none of it makes any sense. Some economics, or rather, basic mathematics is nice to have. But startups are counterintuitive, and hence the only economics you need to know are the economics of scale.
There's a tremendous amount of overlap and shared concepts, but probably going to need to know more about business/finance than economics per se.
Some of the busywork can be farmed off to an accountant/lawyer, but you'll need to understand pricing, unit economics, profit and loss and basic accounting principles. If you're interested in taking investors, you'll need a very good understanding of terms and preferences to avoid getting screwed, and you'll need to be able to talk about business plans realistically to make a pitch. If you start to take on multiple employees, there is a tremendous amount of knowledge (both intuitive and book-learning) about organizational behavior and management that you'll need to internalize.
Economics is mostly theory about how the world should operate based on certain laws... supply and demand etc. They go through rigorous derivations using calculus and statistics. You might get a top level overview of the driving forces behind an industry, but in a startup that's hardly useful.
Also in microeconomics, you are taught how a prototypical consumer might behave under canned conditions. Not at all representative of the real world.
There's really a single law book for running startups, and the first commandment is talk to your customers. Literally everything else is bs, at least in the beginning stages.
Most other answers here are confusing finance or accounting or business-sense for economics... which shows how little they know about economics. And by the way, formal finance and accounting also has little value for an entrepreneur too (just hire an accountant).
My startup partner has a background in marketing and is doing great building the business (while being inept in finance, accounting, technology or economics). If you aren't familiar with marketing, as said above, it's all about knowing your customers.
Other than that knowledge about accounting and being able to read various kinds of reports in particular are highly useful skills as an entrepreneur. That's not economics in the stricter, scientific sense of the word though.
However, it is a very useful framework for thinking when it comes larger abstract stuff like strategy and vision. I use a very basic supply and demand graph and I think you can get pretty far with simply understanding factors that shift those lines.
In addition, economics can get quite political. Again, a general understanding of why it's political can help here, but specifics are not necessary.
All this stuff comes into play once you have already become successful and scaled.
For example, something as simple as supply and demand concepts will make you understand a lot of stuff.
-The Decoy Effect (https://en.wikipedia.org/wiki/Decoy_effect)
The decoy effect highlights the importance of thinking through the structure of tiered product pricing. If you're wondering why newspaper sites like the Economist or WSJ offer digital+print subscriptions that are closely, if not identically, priced to just print subscriptions, this concept helps explain that. Essentially, when you have a menu of prices, carefully creating one or two throwaway options helps make your other offerings seem much more reasonable.
(See the related concept of anchoring below)
For some real world examples, see:
https://www.economist.com/blogs/democracyinamerica/2009/05/t...
http://www.nytimes.com/2006/10/21/dining/21plate.html
-Base Rate Neglect (https://en.wikipedia.org/wiki/Base_rate_fallacy)
This explains why many people ignore general prior probabilities, and focus on specific given probabilities. Give the Wiki a read, there are some pretty stark examples of decision making gone wrong.
A closely related example of this from Bayes' Theorem is the following classic: http://sphweb.bumc.bu.edu/otlt/mph-modules/bs/bs704_probabil...
Base rate neglect can help explain why people dramatically overestimate the accuracy of things like medical tests. Understanding what a "99% accuracy rate" really means can have life changing consequences.
-Sampling Bias (https://en.wikipedia.org/wiki/Sampling_bias)
This serves as a counterpoint to a practice some of the other commentators in this thread have mentioned, i.e. "asking your customers". If your end goal is to serve a diverse set of customers, it's essential that the sample of potential customers you're asking is not biased in some extreme way. For example, asking customers who are only from a specific geographic region, are only of a specific size in terms of headcount, revenue, etc.
I can't find the exact HN discussion, but there was a post that was a stark example of this a few months back. The gist of the post was that someone had built a software business that was able to address a niche accounting problem that many of his local plumbers (electricians maybe?) faced. He grew it to $500,000 in revenue relatively quickly, only to find that very few other plumbers across the country had this accounting challenge. This entrepreneur eventually shuttered his software business, since future prospects for growth were negligible.
-Anchoring Bias (https://en.wikipedia.org/wiki/Anchoring; see in particular the "negotiations" section)
Anchoring has direct applicability in pricing and negotiations. IMO anchoring bias is why if you feel that you are charging too little for your product, raise your prices sooner rather than later. After a certain amount of time, your customers will be "anchored" to that previous price point, and will be quite unhappy with a price increase.
-Sunk cost fallacy (https://en.wikipedia.org/wiki/Sunk_cost#Loss_aversion_and_th...)
This fallacy is quite prevalent in the real world. It's particularly egregious in the defense contracting world, where defense contractors have convinced the US Congress to fund projects that are years behind schedule, and billions over budget. The fallacy can best be described as "throwing good money after bad".
I'd like to note that sometimes this concept is over-applied. If you budgeted $10 for a project, and at the $10 spent mark you discover you need to spend $1 more to complete it, it's not necessarily falling into the fallacy to spend that $1 if the end benefit from that completed project still justifies the overall cost.
It's not the sunk cost fallacy even if the benefit of completion only justified the additional $1 cost; the $10 already spent is irrelevant, since if you choose not to finish, you don't get it back, it's only the sunk cost fallacy if you are treating the cost already spent as a loss of not proceeding.
You sort of did the opposite fallacy, where instead of treating the sunk cost as a loss if you don't proceed, you counted it as a loss if you do. But the sunk cost is neither.
Fair point, I should've said if the total benefit of completing the project is larger than the marginal cost ($1) of completing the project.
> You sort of did the opposite fallacy, where instead of treating the sunk cost as a loss if you don't proceed, you counted it as a loss if you do. But the sunk cost is neither.
Just to be clear, if the total benefit from completing the project is something like $0.50, choosing to spend the $1 to complete the project is an example of the sunk cost fallacy.