Learn · Reading the tape
The City Composite
A float-weighted view of the city's listed companies, expressed in points rather than tradable shares.
Last updated: 2026-09-20
One number for a changing market
The City Composite, shown with the code CITY, combines the city's listed companies into an index. Its base is 1,000 points on August 28, 2026. The engine updates observations by minute and retains daily history for longer comparisons. A level above the base indicates a higher indexed value under its calculation, but the number is not a City Coin balance belonging to any player, fund or institution in the simulation.
The Composite is a description, not a security. MockTradeCity does not provide an Order book for buying or selling the index itself. It helps express what happened across the market without naming every company's price separately. Because the roster can change through listings and delistings, the constituent count shown by the current card is more useful than memorizing a fixed count from an old article or screenshot of the Market page.
Weight follows floating market value
A company's float capitalization is its floating share count multiplied by its price. The Composite adds constituent float capitalizations and divides by an index divisor. A company with a larger float capitalization has a larger weight, so an equal percentage price move contributes more to the index. This is different from averaging every company's percentage change with equal weight or counting how many company symbols finished above their previous closes.
For a simplified illustration, imagine one company represents sixty percent of a basket and another represents forty percent. If the first rises two percent while the second is unchanged, the basket rises about 1.2 percent with shares and membership held fixed. The example explains weighting, not the actual weights of two city companies. A large nominal share price alone is insufficient: the floating share count is the other part of the calculation.
The divisor keeps membership changes coherent
Adding a new company increases the basket's total capitalization even if no existing share price changes. Without an adjustment, that addition could look like a market return. The city adjusts the divisor when basket membership changes so the transition itself preserves the index level. Subsequent price movements then contribute under the updated basket. A halted company can remain in the basket at its last recorded price rather than disappearing merely because trading pauses.
The displayed previous-close comparison values the current basket using its constituents' previous Regular closes and the same divisor. Current and reference levels therefore use a consistent membership basis. This avoids interpreting a newly added listing's capitalization as if existing shares had suddenly appreciated. It also means index comparisons are calculated records, not simply the arithmetic mean of whichever percentage figures happen to be visible in a filtered company table.
Breadth supplies a second view
Market breadth counts advancing, declining and unchanged companies. Each company contributes one to its category regardless of size. The Composite instead gives more influence to larger float capitalizations. A few heavily weighted advances can outweigh many smaller declines, leaving the index higher while more companies are down than up. The reverse can happen when a large constituent declines while numerous smaller companies rise by less influential amounts.
Neither measurement invalidates the other. They answer different questions: how the weighted basket moved and how widely individual price directions were shared. Turnover adds a third view by describing how much City Coin changed hands. Putting these together can distinguish a concentrated move from a broadly shared one, without turning the description into a prediction. The Composite's level alone cannot tell you what happened in every company or in any particular player's Positions.
Where to follow the Composite in the city
The Market page's index card displays the level, point change, percentage change and session landmarks. Its intraday view follows the period relevant to the previous-close comparison, while the longer view uses daily observations. The constituent count identifies the current basket size. Nearby breadth counts show advancing, declining and unchanged companies, letting you compare the weighted result with participation across the roster rather than assuming they must always point the same way.
Daily Wrap preserves a completed day's index figures beside breadth and citywide trading activity. Older dates reconstructed from company closing history may offer only a closing index value and are labeled accordingly; they do not establish an observed intraday high or low. Reading that qualification prevents historical reconstruction from being mistaken for a full live record. Whether shown live or in a recap, the Composite remains a fictional-market measurement in points, with no directly tradable index product attached.