California Population Growth

Instructor: Lauren Posey

Lauren has taught intermediate reading in an English Language Institute, and she has her Master's degree in Linguistics.

In this lesson, you will learn about California's population growth over time, including how it is calculated, and some factors that affect population growth rate.

The Most Populous State

Think about your home state. What is it known for? Every state has aspects that make it unique, and one of California's claims to fame is its population size. Its current estimated population is 39,497,345, and as of the last official census in 2010, it was declared the most populous state. In fact, CA population is large even by world standards--there are only 34 countries that have a larger overall population than this single state!

Even with such a huge population, a steady growth rate is necessary to keep the state economically balanced, such as in the housing and job markets. In order for the state to predict and provide for the needs of its future citizens, constant information about changes in the growth rate and overall population statistics is absolutely vital.

This information is also necessary to keep track of environmental impacts. After all, a larger population requires more land area, and has the potential for greater environmental strain as more resources are needed. Nearby ecosystems can suffer severe negative impacts, especially if the need for habitable land is considered more important than ecosystem preservation.

How Do They Do It?

So how exactly is population growth rate determined? At the most basic level, it has to do with the birth and death rates of a state. Annual birth rate is determined by taking the number of births in a year and dividing it by the total state population for that year. That equation would look like this:

Number of births in a year/total population=Annual birth rate (ABR)

Annual death rate is calculated exactly the same way:

Number of deaths per year/total population=Annual death rate (ADR)

The population growth rate is then determined by subtracting the annual death rate from the annual birth rate:

ABR-ADR=Annual population growth rate

Other Factors

Of course, birth and death rates are not the only factors when looking at population of a state. Another factor is immigration, or the number of people moving into a state, rather than being born there. Over the last 25 years, immigration has made up an average of 58% of California's population growth.

One other factor is emigration, or the number of people moving out of a state. Economics tend to be the strongest motivation for this. For example, California's population growth rate decreased drastically in the early-mid 1990s as a result of the recession. There were fewer jobs available within the state, and so a higher percentage of people emigrated to find work.

CA Growth Rate Over Time

Although the actual rate has varied widely over the years, California has never seen a 10-year period (the amount of time between censuses) without growth. On the whole, it has a very healthy rate of population growth, though a decrease in recent years means that the aging population of the state is greater than the younger population.

The population growth in San Francisco over time reflects the state population growth as a whole
San Francisco Population Growth


California's highest growth rates were during the mid 1800s, when they reached over 15%. This is an excellent example of how immigration can be a major factor in population growth. The majority of the population increase during this time was a result of the gold rush, bringing in thousands of immigrants trying to make their fortune.


The next century of California's history was less dramatic, as far as population growth rate is concerned. The rate of increase slowed and became more steady. This is a huge period of time, so of course there was some variation, but nothing like the previous decade. The rate varied between 5% and 2%, with most decades averaging around 4%. With the gold rush past, the growth rate was determined more by birth and death rates, though of course immigration was a still a major factor.

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