A business is a system

None of them needs special vocabulary or a particular unit. They are lenses. You decide which ones are useful for your business, and what you read in the picture is your interpretation.

Stocks and flows

A stock is something that accumulates. You can point at it and ask "how much is there right now?" Flour on the shelf is a stock. So is steel in the rack, cash in the till and the bank, orders waiting to be made, unpaid invoices, unanswered emails, people on a team, and the skills a team has built up.

A flow is a rate: how fast something enters or leaves a stock. Bags of flour delivered each week fill the shelf. Bags used each day drain it. Sales fill the cash stock, and supplier bills, wages and rent drain it. New orders per week fill the stock of orders waiting, and orders finished per week drain it.

Take the flour shelf in a bakery. The bags on the shelf are the stock. Deliveries add to it, and each day's baking takes from it. The shelf fills when deliveries run faster than baking uses flour, empties when they run slower, and holds steady when the two match. That is all the idea says, and it is enough to ask useful questions. The count on the shelf is not the rate of use. Looking at today's count alone tells you little about whether it is rising or falling.

Three things are worth noticing.

• A stock only changes through its flows. Nothing jumps. If the pile of open orders is bigger than last month, either more came in or fewer went out, or both.
• Stocks give a business its memory and its inertia. A flow can change on a Monday. A stock, such as a backlog, a cash balance or a skills base, takes time to follow.
• Units are yours to choose. A stock can be counted in orders, hours, dollars, kilograms or "roughly a shelf-full". A flow is the same unit per period. The idea does not care which, as long as you are consistent.

Not everything is a clean stock or a clean flow, and some things can be read either way. That is fine. The point is to ask, for any part of your business, "what builds up here, and what moves it?"

Delay and feedback loops

Delay

A delay is time between an action and its visible effect, or between a step finishing and the next one starting. It comes in two common forms.

The first is waiting inside a process. A cake is boxed and finished, then sits on the shelf until the customer comes to collect it. Work is not happening during that time, but the clock is still running for the customer.

The second is lag in information or response. You order flour, and it arrives two days later. You hire someone, and it takes weeks before they are productive. You change a price, and it takes a season before you can tell what happened to orders.

Delays matter because they are easy to forget. A stock that fills slowly looks fine until it does not. A decision whose effect arrives late tempts you to repeat it before the first result has shown up. When a map shows waiting time as its own figure, separate from the time spent doing the work, you can look at it directly instead of guessing.

A delay is not a fault. Some waiting is built in (dough needs to rise) and some is chosen. The map's job is to show where the waiting is and how large it is by your own estimate, so that you can decide whether it deserves a conversation.

Feedback loops

A feedback loop exists when the result of something circles back and affects the thing that produced it. There are two basic kinds.

A reinforcing loop amplifies. More of something leads to more of the same, or less leads to less. A familiar one: good work earns referrals, referrals bring more customers, more customers bring more good-work opportunities. Run backwards, the same loop can slide downward.

A balancing loop pushes back toward a target. A thermostat is the classic: when the room is too cold the heating comes on, and when it warms up the heating stops. In a business, a manager who sees the backlog grow and moves a person onto it is acting as part of a balancing loop. When the backlog shrinks, that person goes back.

Loops are rarely drawn on anyone's wall, yet they are often what makes a business behave the way it does. Combine them with a delay and you get familiar swings: a rush of hiring when work piles up, an idle stretch when the extra hands arrive just as the work eases, then a freeze.

A caution about wording. A loop on a map is a reading. Two things placed next to each other do not prove one drives the other. You might read a sequence of blocks as a loop. Someone else on your team may read it differently. The map makes the disagreement visible, which is where it can be talked through.

Cadence

Cadence is the rhythm of recurring work: daily stand-ups, a weekly shelf count, monthly invoicing, a quarterly review, an annual filing. It is also a flow, a slow and regular one, and it sets the pace at which a business looks at itself.

Two ideas follow. First, work that is triggered by an event (a client calls, an order arrives) rises and falls with demand, while work set by the calendar shows up whether or not anything is urgent. Second, a cadence is also a delay in disguise. If you review prices once a year, then a price that is wrong can stay wrong for most of a year.

Naming the rhythm of each piece of work is a modest act, but it often shows gaps and overlaps that nobody had listed.

Worked example (illustrative)

Maple Street Bakery is invented for illustration. It is not a case study and the figures are not data.

Maple Street Bakery is a neighbourhood shop with a counter, two ovens, a few staff and a Saturday delivery run. It takes special orders, mostly cakes, a few days ahead.

Read as a system, the bakery has three stocks you can see on any given morning.

• Flour on the shelf. Say 12 bags. A normal baking day uses about 2 bags, and the supplier delivers 6 bags twice a week. In and out roughly match, so the shelf stays near the same level.
• Cash. The till and the bank account hold it. Sales fill it. Supplier bills, wages and rent drain it. Wages go out every second Friday, so the drain is lumpy, while sales arrive a little every day.
• Special orders waiting. Say 8 cakes are booked for the weekend. Two new bookings arrive each day, and the bakers finish about two a day, so the list holds steady.

Now picture a week when a large order is booked. Baking uses 3 bags a day instead of 2. The shelf starts to fall. The flour flow in has not changed, and a new order placed today arrives in two days. That gap is a delay. By the time the shelf looks low, the next delivery is already some way off. The cash stock moves too, but later, because the bill for that flour arrives after the flour does.

There are other waits. Dough rises overnight, and nothing is happening to it, but the clock is running. Finished cakes sit in the fridge until the customer comes in. Neither wait shows up in the baker's hours, but the customer lives with both.

You might read one feedback loop in the shop. When the special-order list grows, the owner moves a person from the counter to the ovens. Counter service gets slower, a few walk-in customers leave, and sales ease. When the list shrinks, the person goes back. You might read this as a balancing loop. Whether that is what happens is for the owner and staff to say, not the map.

On the calendar there is a Monday-morning flour order, a daily till count and a wage run every second Friday. That is three rhythms: weekly, daily and fortnightly.

Nothing here says the bakery is doing anything wrong. The picture only lets the people who work there see what they already live with, and talk it over.