In the quest to sharpen our focus on core operations, we recently announced the sale of our Italy commercial services and payments business at a very attractive multiple, over 15 times 2021 EBITDA.
Beginning with global lottery segment, where same-store sales were up over 20% compared to both 2020 and 2019 levels.
In the markets served by IGT's iLottery platform, our lottery same-store sales increased over 60% in 2021, including nearly doubling in the U.S., where iLottery penetration reached 12% in the fourth quarter.
Instant ticket Services had a record year, fueled by a more than 35% increase in standard units produced.
Our PlaySports solution powers over 60 venues in more than 20 states and was recently recognized as the Platform Provider of the Year at the SBC Awards North America.
In addition, casino GGR trends and our sales funnel remains strong in North America, which represents about 70% of our global gaming segment.
In the quarter, we generated over $1 billion in revenue, up 19% year over year on solid global same-store sales growth in lottery, higher replacement unit shipments and ASP in gaming and 25% growth in digital and betting, propelled by continued market expansion and customer demand for our products and technology.
Strong profit flow-through and operating leverage drove adjusted EBITDA to $387 million and the associated margin to 37%, up 31% and 400 basis points, respectively.
The solid financial performance and our rigorous approach to invested capital led to record level cash flow generation with cash from operations of nearly $400 million and free cash flow totaling $326 million, inclusive of favorable working capital performance, part of which is timing with Q1.
In 2021, we delivered over $4 billion in revenue with significant growth across segments versus the prior year.
Strong operating leverage, bolstered by structural cost savings, drove significant increases in profit with over $900 million in operating income and nearly $1.7 billion in adjusted EBITDA, exceeding both prior year and 2019 results.
As we continue to recover from the extreme measures taken during the pandemic, our cost structure is benefiting from the execution of our OPtiMa program, where we overachieved our $200 million cost savings target.
As a reminder, about 3/4 were achieved in our P&L, while 1/4 of that was achieved with structural efficiency in our capital expenditure.
Cash flow generation exceeded our expectations with cash from ops of over $1 billion and free cash flow more than doubling to over $770 million, both record levels.
Revenue increased 30% to $2.8 billion as strong customers' demand drove global same-store sales up over 20% year on year and versus 2019.
As a reminder, extremely high play levels in the first half of '21 were bolstered by certain discrete items, including gaming hall closures in Italy, elevated multi-stage productivity and LMA performance in the U.S. These items contributed about $165 million in revenue and around $140 million of profit.
The high flow-through of same-store sales growth and a positive geographic mix also led to record profit levels with operating income rising nearly 70% to $1.1 billion.
Adjusted EBITDA increasing over 40% to $1.5 billion and operating income and adjusted EBITDA margins of 39% and 55%, respectively.
Revenue rose 33% to $1.1 billion, driven by solid increases in active units, yields, number of machine units sold and ASPs.
Unit reductions in this market of about 840 units year over year and 650 units sequentially were partly offset by increases in the balance of the portfolio.
In the rest of the world, the installed base rose over 380 units year on year and 180 units sequentially, primarily driven by increases in Latin America and plus two units in South Africa.
Global unit shipments increased 62% year on year as operators began increasing capital budgets in the midst of the market recovery.
Shipments totaled 57% of pre-pandemic levels during 2021, indicating there is still some runway to a full recovery in this area, which we don't expect to happen completely until 2023, although we expect North America unit shipments will get close to 2019 levels in 2022.
IGT sold over 23,800 units globally during 2021 compared to about 14,700 units in the prior year and at higher average selling prices.
2021 ASP of over $14,000 exceeded both prior year and 2019 levels on an improved mix of products and new cabinets.
Strong operating leverage, which was accentuated by savings realized from the OPtiMa program, drove a substantial recovery in operating income and adjusted EBITDA with contributions of over $40 million and $170 million, respectively.
Operating income margins in the fourth quarter reached 11%, nearly matching the 12% pre-pandemic level achieved in the fourth quarter of 2019 and are expected to continue to improve in 2022.
The digital and betting segment continues to grow at a fast pace, generating revenue of $165 million in 2021 with double-digit growth achieved in both iGaming and sports betting.
We completed the successful launch of iGaming in both Michigan and Connecticut, and so our sports betting footprint expand to over 60 sports books.
Operating income grew to $33 million, and the operating margin reached 20%, a solid profit contribution from an emerging business and a nice profit flow-through even with increased investments in talent and resources to fund future growth.
Adjusted EBITDA increased to $48 million, more than double the prior-year level.
As I mentioned earlier, exceptional operational performance and disciplined capital management led to a record level of cash generation which, in addition to approximately $900 million in net proceeds from the strategic sale of our Italy gaming business, allowed us to reduce net debt by $1.4 billion.
Leverage is down to 3.5 times, the lowest leverage in company history, and reaching the 2022 year-end leverage target 12 months early.
In Q4, we reinstated a quarterly dividend and implemented a $300 million share repurchase program, the first in company history.
We delivered over $80 million to shareholders during the quarter, including about $40 million in the purchase of 1.5 million shares at an average price of just about $27 per share.
Based on recent SEC filings, you can see we continued repurchasing shares in Q1 with another 570,000 shares repurchased through February 9.
Proactive management of our capital structure continued during the year, as evidenced by the redemption of nearly $1 billion of euro notes.
The refinancing of another $1 billion in U.S. dollar notes at a lower interest rate and the successful amendment and extension of our term loan facility.
The reduced debt, increased liquidity and extended maturities have greatly improved our credit profile and lower interest expense by about $60 million during the year.
Based on the strong performance of 2021 and despite the recent headwinds, we are reaffirming the 2022 full year guidance we provided at the recent investor day.
We currently expect to deliver revenue of approximately $4.1 billion to $4.3 billion, operating income margins of 20% to 22%, cash from operations of between $850 million and $1 billion and capital expenditures ranging from $400 million to $450 million.
Leverage is expected to remain around 3.5 times x in '22 with some variability quarter to quarter.
On a pro forma basis, we see a further improvement in our leverage ratio to the tune of 1/4 of a turn.
In order to provide some indications with respect to the first quarter of 2022, we expect to achieve revenue of $1 billion to $1.1 billion and operating income margins of 20% to 22% in the quarter.

Summary:
Based on the strong performance of 2021 and despite the recent headwinds, we are reaffirming the 2022 full year guidance we provided at the recent investor day.
We currently expect to deliver revenue of approximately $4.1 billion to $4.3 billion, operating income margins of 20% to 22%, cash from operations of between $850 million and $1 billion and capital expenditures ranging from $400 million to $450 million.
In order to provide some indications with respect to the first quarter of 2022, we expect to achieve revenue of $1 billion to $1.1 billion and operating income margins of 20% to 22% in the quarter.