ASX dividend shares: How to snowball your passive income

If you're a fan of dividend investing as a share market strategy, you might have heard of the term 'snowball' to describe the process of building up a stream of passive income from ASX dividend shares.

It refers to the obvious reputation of a snowball rolling down the hill, growing exponentially larger as it collects ever more snow. It's an apt metaphor for how successful dividend investing can work.

The process is simple. First, an investor buys an ASX dividend share that consistently pays out income every six months (or every quarter or every month in some cases).

The investor then adds to the position when they can. But they also reinvest any dividends they receive back into buying more shares. Now that the investor has more shares to their name, the next time a dividend is paid out, they receive even more dividend income. The process is repeated, and the snowball grows ever larger. Eventually, it will be so large that it can help make our investor fabulously wealthy, and perhaps even fund an early retirement.

That's the idea, anyway.

But today, I thought it would be worthwhile to go through how this might actually look in action.

How to get your ASX dividend snowball rolling

We'll use a hypothetical company for this exercise, just to keep things simple. We'll assume that our company starts at $1 per share, and pays out a 4 cents per share dividend in its first year, which we will dutifully reinvest to buy more shares.  Every year, its dividend will increase by 4%, and its share price by 5%, which is roughly in line with what the S&P/ASX 200 Index (ASX: XJO) has historically delivered.

After investing a hypothetical 'life savings' of $15,000 in our first year, we committed to buying an additional 3,000 shares every year. Our rising salary from our day jobs will hopefully help in this regard, given that the cost of buying 3,000 shares will go up 5% annually.

Here's what it looks like if an investor follows this pattern for 35 years:

Passive income compounding in action

As you can see, the effects of compounding start slowly, but become more and more powerful as time goes on. To illustrate, between our first and second year, our investor only got a $172.57 passive income pay rise. But between years 34 and 35, the increase was worth almost $4,000 alone.

Another thing to note is that our investor laid down just over $285,000 in capital over this 35-year period. Yet by the end of it, they had a portfolio worth $1.76 million, spitting out more than $50,000 in passive income annually. That's your snowball in action.

Finally, it is worth noting that this model assumes many things for the benefits of simplification, which aren't accurate to real-life investing. For one, share prices do not go up like clockwork every year. Nor do dividend payments in most cases. One year might see a share rise 12%, only to fall by 8% the next. But for quality companies, and every ASX index fund, the long-term trajectory has always been up. As you can see above, the sooner you start investing in quality stocks or index funds, the wealthier you will be, and the more passive income you will bring in.