** BAR CHART (OR GRAPHS) AND THEIR USES IN ECONOMICS**, What is a bar chart? Bar chart or graph is a graph made up of bars of rectangles which are of equal width and whose lengths are proportional to the quantities they represent.

## features of a bar chart

The major characteristic of the bar chart is that the body of the bars must not touch each other. There must be a space or gap between one bar and another. Bar may be arranged vertically or horizontally.

__Types of bar chart__ or bar graph

__Types of bar chart__

There are three major types of bar charts. These are:

- Simple bar chart
- Component b. charts and
- Multiple ba chart

**Simple bar chart**

Simple b chart is used when the data given are made up of only one item or component

.

The b chart can be presented by tabulated data with evenly spaced bars, separated by gaps with the length proportional to the magnitude of the value given.

**Exemplary use of a simple bar chart** or bar graph

The table represents the quantity of cocoa production in Nigeria between 1960 and 1967. Represent the information or data by a chart.

Table (a): Cocoa production in Nigeria between 1960 and 1967.

Year | Cocoa production (Tons) |

1960 1961 1962 1963 1964 1965 1966 1967 | 7,000 1,500 3,000 6,000 8,500 5,000 4,000 3,500 |

Solution

Table (a): Cocoa production in Nigeria between 1960 and 1967.

Year | Cocoa production (Tons) |

1960 1961 1962 1963 1964 1965 1966 1967 | 7.0 1.5 3.0 6.0 8.5 5.0 4.0 3.5 |

- From the figures given, using the scale: 1cm: 1000 tonnes, the figures can be reduced to simple ones when they are divided by 1000.
- The new values will now be.

__Useful information to be derived from using a bar graph__

__Useful information to be derived from using a bar graph__

- The year with the highest cocoa production can be calculated. The year is 1964
- The year with the least cocoa production can also be calculated. The year is 1961.
- The total cocoa production from 1960 to 1967 can be calculated, i.e. 7,000 + 1,500 + ……… + 4, 000 + 3, 000 = 38,500
- The average or mean production can also be calculated by adding the total production (as in (iii) above) and dividing it by the number of years (8 years), i.e.

7,000 + 1, 5000 + ……. = 4,000 + 3,500

8

=38,500

8 = 4, 812.5 tons/year

##### (b) __what are Component bar chart__

__what are Component bar chart__

A component bar is used when the data involved are of two variables.

**Example**

Represent the population of males and females (in millions) table in towns in Edo State in 1999

Towns | Male (m) | Female (m) | Total (m) |

Uromi | 80 | 60 | 140 |

Ubiaja | 60 | 50 | 110 |

Ekpoma | 70 | 30 | 100 |

Irrua | 30 | 15 | 45 |

Solution

WEED AND THEIR BOTANICAL NAMES

Using a graph sheet, choose a suitable scale for the graph, e.g. 1cm represent 10 units, the graph (component chart above is then drawn. __COMPONENT BAR CHARTS SHOWING THE ____POPULATION ____OF SOME TOWNS__

__MULTIPLE BAR CHART AND USAGE__

__MULTIPLE BAR CHART AND USAGE__

b. Multiple bar charts: The multiple chart is used when there are about three or more variables in a given data. It has multiple bars, each of which stands for a component variable.

Example

Represent Nigeria’s export of cocoa (table 2.7) from Ibadan, Abeokuta and Akure in 1969, 1970 and 1980 by a bar chart.

Table 2.7: Nigeria’s export of cocoa from Ibadan, Abeokuta and Akure in 1960, 1970 and 1980.

Towns | 1960(tons) | 1970(tons) | 1980(tons) |

Ibadan | 30 | 40 | 50 |

Abeokuta | 40 | 30 | 60 |

Akure | 50 | 70 | 40 |

Solution using bar chart

Using a graph sheet, choose a suitable scale for the graph, e.g. 1cm to represent 1o units, the graph (a multiple chart is then drawn.