Apple (NASDAQ:AAPL) stock hit a new high today of $124.43. Adjusted for Apple's seven-to-one stock split, this would have amounted to a stock price of $871.01. Yesterday, when the stock closed above $122, the company's market capitalization of $710.74 billion made headlines as the largest market cap value for any company ever in U.S. history. Given all the doom and gloom headlines about Apple that made rounds just a few years ago as low-cost Android-powered devices increasingly gained market share on iOS, some may feel like they missed the reasons for Apple stock's big rise recently.

Here are the three most important drivers behind Apple stock's growth in the past several years.

1. Soaring iPhone sales
Apple's largest and most profitable business continues to be a winner for the company. The tech giant's most recent quarter was the biggest blowout in a while, with the company reporting unit sales significantly higher than analyst expectations. The record iPhone sales came in at 74.5 million units, 46% higher than Apple's previous record set in the year-ago quarter. At over half of Apple's revenue (69% of revenue in the company's most recent quarter), a healthy iPhone business has a huge positive influence on the company's bottom line.

Data for chart retrieved from SEC filings for quarters shown. Chart source: Author.

2. An aggressive share buyback program
In 2012, Apple announced plans for returning capital to shareholders. The plans included both a regular quarterly dividend and a share repurchase program. Since the initial announcement, both Apple's dividend and its share repurchase program have seen hikes every year. But the company's repurchase aggressiveness with share repurchases outdid its dividend increases by a longshot. The repurchase program has ballooned from an authorized $10 billion to $90 billion. 

The company has spent $73 billion already on share repurchases and has said it is going to announce an update to its program in April.

AAPL Average Diluted Shares Outstanding (Quarterly) Chart

AAPL Average Diluted Shares Outstanding (Quarterly) data by YCharts

Thanks to Apple's ability to aggressively repurchase its own shares with its heady cash flow, earning per share is growing faster than net income. In Apple's first fiscal quarter in 2015, Apple's net income was up 37% while its EPS was jumped 48%.

3. Continued pricing power
It was the forecast for declining pricing power that served as the crux to the most commonly cited bear case for Apple when shares pulled back in the second half of 2012 and into 2013. Apple's diminishing pricing power, critics argued, would put an end to the company's hefty gross profit margins. But what has the proliferation of cheap Android devices done to Apple's pricing power? Nothing.

Critics were dead wrong.

Data for chart retrieved from SEC filings for quarters shown. Chart source: Author.

Thanks to higher storage capacity tiers and the company's iPhone 6 Plus with a $100 premium to any flagship iPhone yet, Apple's average selling price actually increased in the company's fiscal first quarter from the year-ago quarter. And while Apple's gross profit margin may never return to levels reached int he first half of 2013, it has stabilized at a very high level as the company continues to benefit from significant pricing power.

Apple stock's 62% rise in the last 12 months was fueled by a combination of a bear case that had suppressed the stock and subsequently never panned out, and the company's continued success at growing intrinsic per share value through repurchases and income growth.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.