What is the expected organic growth rate for the Tower segment in 2021 
ifying where wireless networks are going and investing early to position the company to capitalize on future opportunities, as we have done with small cells, edge computing and CBRS.
One of the core principles underpinning our strategy is to focus on the U.S. market, because we believe that represents the best market in the world for wireless infrastructure ownership, since it has the most attractive growth profile and the lowest risk. And we believe this dynamic of higher growth and lower risk will continue into the future, which is why we expect our U.S. based strategy will drive significant returns for shareholders.
With that in mind, we have invested nearly $40 billion in towers, small cells and fiber assets in the top market that are all foundational for the development of future 5G network. We believe our unique strategy, portfolio of the infrastructure assets and proactive identification of future opportunities provide a platform for sustained long-term dividend growth as wireless network architecture evolves and our customers' priorities shift over time.
Today, our customers are primarily focusing their investment on macro sites as towers remain the most cost-effective way to deploy spectrum at scale and established broad network coverage. With our high quality towers concentrated in the top markets, we are clearly benefiting from this focus with an expected 6% organic growth for our Tower segment in 2021 and an expected 20% increase in tower core leasing activity next year when compared to these 2021 levels. With history as a guide, we believe the deployment of additional spectrum on existing cell sites will not be enough to keep pace with the persistent 30% plus annual growth in mobile data traffic.
As a result, we expect cell site densification to remain a critical tool for carriers to respond to the continued growth in mobile data demand as it enables our customers to get the most out of their spectrum assets by reusing the spectrum over shorter and shorter distances. When the current cell site upgrade phase shift to densification phase, we believe the comprehensive offering of towers, small cells and fiber will be critical for our customers and provide us with an opportunity to further extend the runway of growth in our business.
While we expect the densification phase of build out will drive additional leasing on our tower assets for years to come, we believe small cells will play an even greater role as the coverage area of cell sites will continue to shrink due to the density of people and therefore the density of wireless data demand. With more than 80,000 small cells on air or committed in our backlog, high capacity fiber assets and the vast majority of the top 30 markets in the U.S. and industry-leading capabilities, we believe we are well positioned to deliver value to our customers as their priorities evolve, driving meaningful growth in our small cell business.
Bigger picture, when I consider the durability of the underlying demand trends we see in the U.S., how well we are positioned to consistently deliver growth through all phases of the 5G build out with significant potential upside in our comprehensive asset base as wireless networks continue to evolve. Our proven ability to proactively identify where wireless network architecture is heading and to be an early investor in solutions to help future networks, the deliberate decisions we have made to reduce risks associated with our strategy and our history of steady execution.
I believe that Crown Castle stands out as a unique investment, that will generate compelling returns over time. In the near term, as I mentioned before, we expect to deliver outsized AFFO per share growth of 12% in 2021. We expect to generate 8% growth in AFFO per share in 2022 at the high end of our long-term growth target and supported by an expected 20% increase in tower core leasing activity and we increased our common stock dividend by 11% for the second consecutive year.
Longer term, we believe Crown Castle provides an exciting opportunity for shareholders to invest in
ifying where wireless networks are going and investing early to position the company to capitalize on future opportunities, as we have done with small cells, edge computing and CBRS.
One of the core principles underpinning our strategy is to focus on the U.S. market, because we believe that represents the best market in the world for wireless infrastructure ownership, since it has the most attractive growth profile and the lowest risk. And we believe this dynamic of higher growth and lower risk will continue into the future, which is why we expect our U.S. based strategy will drive significant returns for shareholders.
With that in mind, we have invested nearly $40 billion in towers, small cells and fiber assets in the top market that are all foundational for the development of future 5G network. We believe our unique strategy, portfolio of the infrastructure assets and proactive identification of future opportunities provide a platform for sustained long-term dividend growth as wireless network architecture evolves and our customers' priorities shift over time.
Today, our customers are primarily focusing their investment on macro sites as towers remain the most cost-effective way to deploy spectrum at scale and established broad network coverage. With our high quality towers concentrated in the top markets, we are clearly benefiting from this focus with an expected 6% organic growth for our Tower segment in 2021 and an expected 20% increase in tower core leasing activity next year when compared to these 2021 levels. With history as a guide, we believe the deployment of additional spectrum on existing cell sites will not be enough to keep pace with the persistent 30% plus annual growth in mobile data traffic.
As a result, we expect cell site densification to remain a critical tool for carriers to respond to the continued growth in mobile data demand as it enables our customers to get the most out of their spectrum assets by reusing the spectrum over shorter and shorter distances. When the current cell site upgrade phase shift to densification phase, we believe the comprehensive offering of towers, small cells and fiber will be critical for our customers and provide us with an opportunity to further extend the runway of growth in our business.
 While we expect the densification phase of build out will drive additional leasing on our tower assets for years to come, we believe small cells will play an even greater role as the coverage area of cell sites will continue to shrink due to the density of people and therefore the density of wireless data demand. With more than 80,000 small cells on air or committed in our backlog, high capacity fiber assets and the vast majority of the top 30 markets in the U.S. and industry-leading capabilities, we believe we are well positioned to deliver value to our customers as their priorities evolve, driving meaningful growth in our small cell business.
Bigger picture, when I consider the durability of the underlying demand trends we see in the U.S., how well we are positioned to consistently deliver growth through all phases of the 5G build out with significant potential upside in our comprehensive asset base as wireless networks continue to evolve. Our proven ability to proactively identify where wireless network architecture is heading and to be an early investor in solutions to help future networks, the deliberate decisions we have made to reduce risks associated with our strategy and our history of steady execution.
I believe that Crown Castle stands out as a unique investment, that will generate compelling returns over time. In the near term, as I mentioned before, we expect to deliver outsized AFFO per share growth of 12% in 2021. We expect to generate 8% growth in AFFO per share in 2022 at the high end of our long-term growth target and supported by an expected 20% increase in tower core leasing activity and we increased our common stock dividend by 11% for the second consecutive year.
Longer term, we believe Crown Castle provides an exciting opportunity for shareholders to invest in