Last but definitely not least, is Evolution Mining. Lawrie Conway, who is Managing Director and Chief Executive Officer. Lawrie has over three decades of experience in the resources sector across a range of operational, commercial, and financial roles. Lawrie has held several senior leadership positions, including CFO at Evolution. Before joining Evolution in 2014, Lawrie worked at Newcrest and BHP, gaining extensive experience across Australia, Papua New Guinea, and Chile. Lawrie?
Thank you, Andrew. Good morning, everyone. Firstly, to Jim Walker and the Diggers & Dealers Mining Forum team, thank you for the opportunity to present here today in I am sure what will be another successful forum. Also, congratulations on the new permanent facility. It certainly has upgraded the forum, and I look forward to many more years of using that. Thank you to Andrew and Canaccord Genuity for your ongoing sponsorship and support of the forum as well. Before getting into the full detail of the presentation, there are the forward-looking statements that are customary. We do have reserves in here, and we also do have some forward-looking financials, which you need to take with caution. Before getting into the details of the economy and our assets, I did want to spend some time on one of our more important assets, which are our people.
Last year, I put this slide up here, which is the new plant that we had built at Mungari. When we built that plant, I gave you the story of that tank, which was really around mental health. At each of our operations, we have things like this that highlight the mental health aspects of working in an industry that is high intensity and certainly at times can be a lonely environment. I didn't want to leave it there last year and not come back to that this year, because when we put that in, it wasn't just because we had built a new facility and we had that tank that we decided we wanted to paint. The reason for that, if you look at it, across our business at Evolution, 30% of our workforce is fly in, fly out, drive in, drive out.
That means just around 1,100 people of our workforce, each and every time they come to work, they are leaving their family and friends at home for a week or two at a time, and they are working in isolation. What we need to be cautious of and conscious of is how do we make sure that it is the right working environment for them? When you look at some of the statistics, our employee assistance program that we have, 50% growth over the last 12 months has been going into those call centers across our business. In the last two years, that is 100% increase in the amount of calls that we have been receiving into that center. When you look down a little bit deeper into that, two-thirds of those calls are related to personal issues.
We do have people in our business that are calling out to our call centers, asking for help on a personal sentiment rather than work-related issues. As you can see, a number of agencies and service providers that we do use across our business is to provide that support, not just for our fly-in, fly-out, drive-in, drive-out workers, for our entire workforce, to make sure that each and every day they're able to perform their job to the best of their ability, but to also have the right work-life balance and the mental health balance. Shifting a little bit now and looking at the global economy in which we're dealing with.
I think when you look and listen to what the Honorable Joe Hockey said this morning, world order is changing, and I think he was very accurate in terms of what that does mean for economies going forward, but also what it does mean for the mining industry. Unfortunately, as this world order is changing, it is positive for the mining industry. When you look at it in the precious metals, there has been a shift away from globalization, and there's a change in world order. If you look at the charts on the right, just to explain what they are, that is two years ago, the long-term average consensus pricing for gold and copper sat at about $1,800 an ounce and $3.90 a pound.
That was saying in about 2028, 2029, that would be the long-term average price that would be achieved. Two years on from that, you've seen the long-term gold price more than double to now $3,650 an ounce, and you've seen a 40% lift in the long-term copper price to $5.40 a pound. If you're to take recent projections around supply and demand for copper, that $5.40 is only going to go up over the next 12 to 18 months. Therefore, that's what you're seeing, a shift in the change in the world order. The de-globalization is going to be good in terms of metal prices. What you're also seeing, and I'll show a little bit later, is a rebalancing of reserves. Central banks around the world are moving away from holding U.S. Treasuries towards holding gold, so therefore that is good for gold.
The U.S. national debt that the Honorable Joe Hockey talked about this morning, it's currently sitting at $40 trillion. To put that into perspective, that, when we presented at the Macquarie Conference three months ago, was sitting at $39 trillion. In three months, the U.S. debt has gone up by $1 trillion. That is the equivalent of $11 billion a day increasing in debt in the U.S. economy. The rate of the U.S. spending is certainly not expected to change. As was also talked about this morning, the amount of money that is going into defense in the U.S. is increasing, and they're not offsetting that with spending cuts elsewhere. That defense spending is certainly good for critical and base metals. The average U.S. interest cost per day is now sitting at $3 billion.
Just to put a little bit of other perspective, in Australia, our debt interest cost every day is now sitting at around AUD 66 million a day. Each and every day, the Australian government has to find ways to service that debt, and that's the problem that Joe talked about this morning in terms of the Australian government spend rate is certainly exceeding the revenue take. As I've said, confidence is eroding, and the strategic allocation has changed. What does that mean if you look at it? Central banks. This has been the amount of gold purchases by central banks over the last few years. When you look at the first quarter of this year, record gold prices around $5,500 an ounce, then certainly the uncertainty going on in and around the Middle East certainly slowed down the buying in that first quarter.
If you look at the second quarter, at just under 300 tons, that certainly does say that we're on track again for this year to get up to 1,000 tons of gold purchases by the central bank. What does that show us? It shows us that that allocation of capital by central banks is shifting away from Treasuries into gold. For the first time a couple of months ago, since 1996, central banks have held more gold in reserves than they have held in U.S. Treasuries. If you look back in the early 1990s, the gold holdings were around 50%. There's certainly a long way to go for central banks in terms of how much they hold in gold.
When you overlay it with what the governments, which does go to their spending, the percentage of debt as a percentage of GDP is continually elevated and is only going to get higher. For that is creating certainly no flexibility in policy for the governments. Again, that's going to what Joe said this morning. The more you spend without having that increasing in revenue and living within your means and lowering your reliance on debt, you certainly are going to create those problems. When you look at it, the headlines are changing, but the environment hasn't. This is the U.S. national debt. It rolls over by $11 billion a day.
As I said, if you look at it, one of the greater concerns at that $40 trillion is that $8 trillion or 20% of that debt rolls over within the next 12 months. The U.S. government has to either refinance that, they certainly won't be able to repay it, and therefore that is putting more and more pressure on the U.S. Treasuries. There's been different events. You look over the last six years, be it through COVID, the Ukraine War, the inflation shock as we came out of COVID and rebounded very strongly, then the trade fragmentation and the Middle East conflict. All of these things are different events over the last six years, but you're still getting similar responses.
You're increasing your debt, you're creating more geopolitical stress, the central banks are starting to demand more in gold, which, if you're a gold producer, is a great place to be. If you're a gold producer in these times, the safest bet is to have a high margin business. Thank you, Andrew, to your team at Canaccord for the great research. It's not paid publicity, but if you look at it, they have looked at the industry from 2015 through to now, so the last 12 years, and looked at that margin. You can see that the margin has been increasing. At Evolution Mining, our margin in each and every one of those 12 years, our margin has exceeded the industry average. It means we are generating more cash per ounce of gold that we produce than anyone else in the industry.
If you look at the last two years, that increasing margin is, yes, on the back of the rising gold price, but what it is also linked to is a differentiation in our portfolio, which is where we hold copper. What that does is if you have a look at it, is that top line is showing the margin addition generation that copper is providing to our business. If you go back to FY 2021, 2022, that lift from AUD 350 million to AUD 769 million, that's when we took 100% ownership of Ernest Henry. When you look at that shift from AUD 908 million to AUD 1.316 billion, that's when we took ownership of the Northparkes operation.
When you look at it against the achieved copper price, having that proportion of our portfolio with copper in a rising copper price environment is certainly adding to that margin that we're having in the business. We achieved a rate of AUD 5.73 per pound through FY 2026, the spot price today sits at AUD 6.34. If that was to hold for this year alone, that would add between AUD 130 million and AUD 140 million of additional cash flow to our business at Evolution. When you look at it, we've got about 22% of our revenue is coming from those two assets at Ernest Henry and Northparkes. If you look at them just as copper assets, they are high margin assets with their C1 costs around AUD 0.65 and AUD 1.23 a pound against a spot price of AUD 6.34.
Just as importantly though, at these assets, we've got around 3 million tons of latent mill capacity. We are constrained by our mine at the moment, what we are doing there is looking at options to further grow our production. If you look at Ernest Henry, last week, we announced the acquisition of the Carnaby Resources, which will give us about an additional 10,000 tons of copper at Ernest Henry, lifting their production rate by about 20%. In February this year, we approved the Bert Underground mine to be developed at Ernest Henry, that will fill the mill by about another 10%. We've picked up a lot of land in and around Ernest Henry from Rio Tinto and others, whereby, we're now drilling out in those areas that are all within trucking distance to fill that latent capacity at Ernest Henry.
Meanwhile, at Northparkes, in February, we approved the E22 Block Cave, which will allow us to go above the 7.5 million ton processing rate that we have at Northparkes. We've kicked off a study that can look at lifting that production rate by 40% to 100%, so anywhere between sort of 10 million-15 million tons per annum at Northparkes. As I said earlier, when you look at the outlook for the long-term copper price, bringing on that production in about two to three years' time will only further add benefit to our business. It's not only in those two assets that we are investing. What I look at across the portfolio is what rate of return can we generate for our shareholders when we make a decision to invest in the business?
We invested about AUD 1.1 billion across the business last year. When you look at it, at the bottom of that chart there, the Evolution Mining average. Since we've owned all of these assets over the last 10 years, the average annual rate of return out of those assets has been 18%. That is at a metal price that is a lot lower than what the spot prices are today. When you look at all of the projects that the board has approved over the last 12 months at Cowal, Northparkes, and Ernest Henry, every one of those assets will generate a rate of return that is higher than 18%. When you look at the green bars there that ranges from 23%-77%, they are at gold prices that are anywhere between 40% and 50% below the current spot prices.
That's what the gold bars represent, that if we are delivering those projects and they come into production at spot prices, we can get up to 128% rate of return out of those projects. So it confirms the high-quality portfolio that we've got, the high margins that we've got, and also the good mix between gold and copper into our production. I want to just bring it in a bit closer to Mungari here in W.A. In June of 2023, the board backed the recommendation of management to invest in expanding the operation from 2.1 million tons to 4.2 million tons per annum. If you recall, in June of 2023, the gold price was certainly a lot lower. Inflation was running high. It was a tight labor market. Our turnover rate at Mungari was sitting at around 38%. It is now sitting around 15%-16%.
The board made the decision to invest in that operation at Mungari. What we have been able to do, as I said last year, we delivered that project early. We've delivered it under budget, but we have now successfully commissioned and ramped that up. This is Castle Hill, where that pit is now fully operational, and we're in Stage I and Stage II there. We've also completed the haul road from Castle Hill down to the plant. We made a conscious decision to increase the capital allocation to fully seal that road, so it becomes a 24/7, not weather-dependent haul road. Therefore, we can continually supply 80% of our feed for Mungari through that sealed haul road from Castle Hill.
We finished the plant, as I said, early, and it is now fully ramped up and running at the 4.2 million tons per annum rate. Lastly, when you look at it, why Evolution? In 2026, the year that we've just finished, we generated record cash flow of about AUD 1.4 billion, at a margin of AUD 2,000 an ounce after, as I mentioned earlier, we have invested AUD 1.1 billion into our business. We've increased our production threefold since we've started acquiring assets over the last 10 years, we've averaged a rate of return, as I mentioned earlier, of around 18% per annum.
When you consider we're generating that 18% per annum, those projects that we're now investing in that are going to generate much higher rates of return, our margin of AUD 2,000 an ounce says that we can sustain that when you look at our reserve mine life of 17 years. We can deliver those cash flows each and every year if these metal prices stay at where they are. We've increased our ore reserves by 43% on a per share basis, we've paid over AUD 2 billion in dividends on a very good policy, which is based on free cash flow, and we pay out at a 50% payout rate. With that, thank you for your time today.
Thank you.