What is the estimated gross margin for Xiamen fab in 2022
 we foresee those structural catalysts will continue to drive, including the 5G transformation, the EV and IoT devices. And those megatrends are still representing significant growth on a year-over-year basis. And we do anticipate those structural drivers will continue to fuel our growth including the OLED driver, the ISP, the WiFi-6, RF switch, MCU, PMIC, and so -- and which also lead to a higher silicon content. So we are convinced that most of those demand surge are here to stay largely driven by those structural needs.
So given those catalysts, and we have certain confidence. And -- I mean, in addition to that, based on our efforts and market position, that gives us that confidence that the 2022 will be another strong year for UMC to gain market share.
Charlie Chan -- Morgan Stanley -- Analyst
Yes. But the consensus for TSMC is like next year to grow 15% to 20%. So do you think you can perform similar or even better than this key foundry peer?
Jason Wang -- Director and President
Our estimate on the foundry industry growth in 2022 at this point is about 12%.
Charlie Chan -- Morgan Stanley -- Analyst
12%. I'm sorry. Okay.
Jason Wang -- Director and President
12%. Yes. And for our business outlook, I think we'll be higher than this current foundry industry projection.
Charlie Chan -- Morgan Stanley -- Analyst
Okay. And lastly, variable cost. I mean that is a key reason why foundry peers want to hike the price, right? So variable cost no matter percentage or per wafer number. So can Chitung give us some kind of comment about the trend? For example, this year-over-year, what was the growth for the variable cost? And what would be the variable cost growth for the coming two years?
Qi Dong Liu -- Chief Financial Officer, Senior Vice President, Head of Corporate Governance and Company Secretary
Yes. For the operating expenses, it will be growing along with our enlarged revenue. However, as a percentage of revenue, we hope it will be flat to down, under control. So the revenue growth will outpace the operating expenses. As for raw material like raw wafer and also labors that were also on the rise. But altogether, I think we are commenting that because of our production efficiency improvement, our improved economy of scale, and also with a good outlook for both demand as well as pricing for 2022. I think there's still further upside for our margins -- profit margins.
Charlie Chan -- Morgan Stanley -- Analyst
Got you. Thank you that's super helpful. Thanks gentlemen.
Operator
The next question is coming from Roland Shu of Citigroup. Go ahead please.
Roland Shu -- Citigroup -- Analyst
Good afternoon. So your Xiamen fab began production from 4Q 2015. It was still loss-making last year, and I think it is still loss-making now. So with the better pricing, when do you expect Xiamen fab is going to be turned around? And also how many margin upside or earning upside to UMC once Xiamen fab is breakeven?
Qi Dong Liu -- Chief Financial Officer, Senior Vice President, Head of Corporate Governance and Company Secretary
Xiamen should be able to be profitable in 2022. As a matter of fact, they are profitable in single quarters of 2021. So we are very close to breakeven in 2021. And it is expected to be profitable in 2022. However, it will still below corporate average in terms of profit margin in 2022. And there's still room for Xiamen to catch up to the level of UMC's corporate average.
Roland Shu -- Citigroup -- Analyst
Understood. Yes. Do you have the time frame of when this Xiamen fab gross margin is going to approach corporate average?
Qi Dong Liu -- Chief Financial Officer, Senior Vice President, Head of Corporate Governance and Company Secretary
No, we don't have a time frame. We -- all we can say is I can give you a rough comparison. Currently, our Singapore fab has higher gross margin than corporate average. And the Japan fab is catching up to almost identical to the UMC corporate average. And the Xiamen is, as I mentioned, coming out of loss-making to nearly breakeven this year. And it will be profitable next year, but still away 
 we foresee those structural catalysts will continue to drive, including the 5G transformation, the EV and IoT devices. And those megatrends are still representing significant growth on a year-over-year basis. And we do anticipate those structural drivers will continue to fuel our growth including the OLED driver, the ISP, the WiFi-6, RF switch, MCU, PMIC, and so -- and which also lead to a higher silicon content. So we are convinced that most of those demand surge are here to stay largely driven by those structural needs.
So given those catalysts, and we have certain confidence. And -- I mean, in addition to that, based on our efforts and market position, that gives us that confidence that the 2022 will be another strong year for UMC to gain market share.
Charlie Chan -- Morgan Stanley -- Analyst
Yes. But the consensus for TSMC is like next year to grow 15% to 20%. So do you think you can perform similar or even better than this key foundry peer?
Jason Wang -- Director and President
Our estimate on the foundry industry growth in 2022 at this point is about 12%.
Charlie Chan -- Morgan Stanley -- Analyst
12%. I'm sorry. Okay.
Jason Wang -- Director and President
12%. Yes. And for our business outlook, I think we'll be higher than this current foundry industry projection.
Charlie Chan -- Morgan Stanley -- Analyst
Okay. And lastly, variable cost. I mean that is a key reason why foundry peers want to hike the price, right? So variable cost no matter percentage or per wafer number. So can Chitung give us some kind of comment about the trend? For example, this year-over-year, what was the growth for the variable cost? And what would be the variable cost growth for the coming two years?
Qi Dong Liu -- Chief Financial Officer, Senior Vice President, Head of Corporate Governance and Company Secretary
 Yes. For the operating expenses, it will be growing along with our enlarged revenue. However, as a percentage of revenue, we hope it will be flat to down, under control. So the revenue growth will outpace the operating expenses. As for raw material like raw wafer and also labors that were also on the rise. But altogether, I think we are commenting that because of our production efficiency improvement, our improved economy of scale, and also with a good outlook for both demand as well as pricing for 2022. I think there's still further upside for our margins -- profit margins.
Charlie Chan -- Morgan Stanley -- Analyst
Got you. Thank you that's super helpful. Thanks gentlemen.
Operator
The next question is coming from Roland Shu of Citigroup. Go ahead please.
Roland Shu -- Citigroup -- Analyst
Good afternoon. So your Xiamen fab began production from 4Q 2015. It was still loss-making last year, and I think it is still loss-making now. So with the better pricing, when do you expect Xiamen fab is going to be turned around? And also how many margin upside or earning upside to UMC once Xiamen fab is breakeven?
Qi Dong Liu -- Chief Financial Officer, Senior Vice President, Head of Corporate Governance and Company Secretary
Xiamen should be able to be profitable in 2022. As a matter of fact, they are profitable in single quarters of 2021. So we are very close to breakeven in 2021. And it is expected to be profitable in 2022. However, it will still below corporate average in terms of profit margin in 2022. And there's still room for Xiamen to catch up to the level of UMC's corporate average.
Roland Shu -- Citigroup -- Analyst
Understood. Yes. Do you have the time frame of when this Xiamen fab gross margin is going to approach corporate average?
Qi Dong Liu -- Chief Financial Officer, Senior Vice President, Head of Corporate Governance and Company Secretary
 No, we don't have a time frame. We -- all we can say is I can give you a rough comparison. Currently, our Singapore fab has higher gross margin than corporate average. And the Japan fab is catching up to almost identical to the UMC corporate average. And the Xiamen is, as I mentioned, coming out of loss-making to nearly breakeven this year. And it will be profitable next year, but still away 