Why Do Stock Prices Go Up?

Dr Ajibola Awolowo

The stock market is a place where the shares of various companies are traded everyday. When we go to the stock market and buy the shares of any company, we become an owner of the company into which we have bought.

There are various reasons why people buy shares in any given company. Some want to get a regular income in the form of dividends while others want to buy a big enough stake in a company in order to get a seat on the board. One thing, however, that is common to all buyers of shares is that we hope the price of the shares go up after we buy. Almost no one buys shares in a company and thereafter prays for the price to decline massively.

This thought led me on a quest to understand why and how the prices of companies go up. Understanding this is key to decipher if any price rise is sustainable or fleeting.

One of the oldest and most basic formulas used in investing is that for Price/ earnings ratio (P/E Ratio). It is not clear who developed this metric, but the formula is below:

P/E Ratio = Price/ Earnings

P/E Ratio is obtained by dividing the price of a company share by the Earnings of the same company. The answer is a number which when low, may mean that the company is selling at a discount presently and when high, the company may be selling at a premium. The P/E ratio of an asset is the multiple of the assets earnings at which investors are willing to buy the asset.

By making Price the subject of the above formula, the relationship between the P/E ratio and the earnings become clearer.

Price = Earnings * P/E ratio.

Therefore, in determining the price of any asset, there are 2 variables. These are the earnings of the asset and the P/E ratio.

For the price of any company to go up in a sustainable fashion, one or both variables, need to be on the increase. Any increase in price that is not backed up by verifiable and sustainable increase in any of these 2 variables is doomed to fail.

Therefore, the major question we need to ask ourselves then is how can the earnings of a company and its P/E ratio be sustainably increased?


The earnings of a company is the profit or loss recorded after all costs/ expenses and tax has been charged to a company revenue for a calendar period. This can be found on the statement of profit/ loss of every company. The profit for the period can further be divided by the total outstanding shares in circulation to obtain the Earnings Per Share (EPS) which is how much is earned by each shareholder of the company for every unit of the company he or she holds.

How can earnings be increased?

  1. By increasing revenues: Companies can increase their revenue by selling more of their product or service (increasing volume) or by increasing the price of goods sold or services rendered. Due to immense competition, only companies that have a competitive advantage can sell more products and increase the price of their goods sustainably. When companies that lack this increase their price, their customers switch to an alternate product or service. Revenues can also be grown by setting up a new subsidiary that thrives and by acquiring or merging with another business.

Note that one-off increase in revenues by asset disposal is not sustainable and should be disregarded when assessing for revenue growth in a company.

  • Cost reduction: If a company is unable to persistently grow its revenue, it can generate more earnings by reducing its costs. Unfortunately, this approach to growing earnings is not sustainable as inflation will always lead to rising costs of raw materials needed to produce the good. Growing earnings by cost moderation can only work if the rate of cost growth is less than the rate of inflation.
  • Reducing the outstanding shares in circulation: Even in the face of constant revenues, rising inflation and even stagnant profit after tax, companies can still increase their Earnings Per share by reducing the number of outstanding shares. They do this by ‘share buy-backs’ in which the company buys and retires its own shares. The number of slices that the pie needs to be cut into reduces and each subsequent slice appears bigger even though the size of the entire pie has remained the same. Recently, we have seen Dangote Cement undergoing the share buy-back program on the Nigerian Exchange and a subsequent increase in the price of each share of the company.


The P/E ratio is the multiple of earnings at which investors are willing to buy the asset that generates the earnings. Many things can lead to an increase or decrease in the P/E ratio of a company. Some of them are sustainable while others are not.

Unsustainable reasons

  1. General market euphoria as seen during bull markets can lead to rapidly expanding P/E ratios. An example of this was seen on the Nigeria Stock Exchange in 2008 when P/E ratio of some companies rose to well over 50 from an average of 15 previously. In times of bear markets, the converse is true. In the 2020 crash, we saw the PE ratio of some excellent companies at 1.7.

Rapid changes in the PE ratio brought on by extremes of market sentiments are unsustainable as the market eventually recognises its error and corrects them.

  • When the market anticipates a dividend or bonus share issue by a company, investors bid up the price. None of these corporate actions, however, lead to an increase in the future earnings of the business or a sustainable rise in the P/E ratio. This rise in P/E ratio is therefore very short lived and driven by sentiments.

Sustainable Reasons

When a company has constantly grown its revenues and earnings over a long period of time, thereby showing that this rise is sustainable, investors would be willing to pay a higher multiple of the earnings to buy the company. This translates to a sustainable rise in the company’s P/E ratio which is driven by the proven sustainable rise in earnings.

An example of this is shown by Okomu Oil Palm Company. In 2010, its revenue was about N6 billion, profit after tax was about N1.6 billion, earning per share was about N3.4, Price per share as at 31st December 2010 was N7.6 which translates to a P/E ratio of 2.2.

Fast forward to 2020 and its revenue is now N23.4 billion, profit after tax now N7.5 billion, earning per share now N8.16, Price per share as at 31st December 2020 was N91 which translates to a P/E ratio of about 11.

On the surface, this looks incredibly good when you consider the expansion in PE ratio from 2.2 to 11 over a 10-year period. However, there is still a lot hidden. In 2010, total out standing shares were approximately 500 million units while in 2020, we had approximately 1 billion units in circulation. If we adjusted for this, the P/E ratio expansion would be much more pronounced.

Before you buy that company shares in search of capital appreciation, ask yourself if what you want is sustainable price increase or just volatility. If you want sustainable capital appreciation, does the company presently have or show potential for good revenue growth, modest cost, growing earnings and ultimately, an expanding P/E ratio? You need to be brutally honest with yourself.

You cannot answer these questions objectively if you have not done extensive research into that company and looked at their past results over a minimum of 5 years.

In summary, Sustainable increase in share prices is because of earning growth and P/E ratio expansion over time. Short term price volatility, from dividends and bonus issues, is often not sustainable and prices usually reverts to the mean.  It is only when investments are considered in the long term can the dual forces of earning growth and P/E ratio expansion work their magic on share prices.

Ajibola Awolowo


4 thoughts on “Why Do Stock Prices Go Up?

  1. Thanks for this enlightenment. I really enjoyed reading this article. The knowledge acquired is a life long asset.

Leave a Reply

Your email address will not be published.

WP Twitter Auto Publish Powered By : XYZScripts.com