Principally not. Principally and eventually once the business normalizes, we should approach normal levels of gross margins. Now having said that, the definition of gross margin is, of course not identical across the industry, okay, so – it always depends what is in SG&A and what is in gross margin, but having said that, the great equalizer is operating income obviously and we expect a significant shift there, but driven heavily by gross margin expansion in CRS. 
Josef H. von Rickenbach - Chairman & Chief Executive Officer
The profitability is actually very promising, okay. So of course, you would not deduce that given where they have now been in the startup range. But overall, we expect that we can achieve our goals well in this new environment. And in terms of the size and how much they make up, while oncology has been an important indication and therapeutic area for us for a long time and it would be well over 25% of the total backlog, again buoyed actually by this quarter's new business performance. And overall the backlog would probably be – if I had to give you sort of a guess, I don't have an exact number, but I would say at least a north of a third if not approaching 40%.

Operator
Thank you. Our next question or comment comes from the line of Steven Valiquette from UBS. Your line is open.
Steven J. Valiquette - UBS Securities LLC
All right. Thanks. Good morning, Joe and Ingo. So I think you as guys mentioned a good news here is that your revenue growth actually your largest customer seems to be witnessing some nice acceleration. But I do have a couple of questions on that largest customer for a minute, anyway.
And I guess, first when we talk about the expected sales acceleration in the CRS segment over the next two to four quarters, just want to confirm whether or not that includes the sales trend that you expect from that largest customer as well. So that's the first question. And then, the second one, I think some investors maybe are still wondering about this, maybe just some close around this topic. Is there any possibility that this third CRO partner brought on by your largest customer may ultimately be hurting your own sales trend lines with that customer or is that not really a factor on what's happening here? Thanks.
Josef H. von Rickenbach - Chairman & Chief Executive Officer
Yeah, hi, Steve. Yeah, so basically – I think I alluded to some of this already before. But just to take the second question upfront. No, we don't expect the third player to hurt us. I think overall outsourcing is going to increase and especially where we're at right now, I wouldn't say that we are sort of the first target anyway.
Overall, we believe that we are in a good place with this client and if you kind of put them into the context of our top five clients, I think they're at a point where they are stabilizing and where we basically can maintain or even grow the backlog that we have with them.
Steven J. Valiquette - UBS Securities LLC
Okay. On that first part though again as far as the sales ramp, I think just your raw sales with that largest customer I think (1:06:27) lowest this quarter it's been since like mid 2012. So just on a raw basis, forget about a percent for a moment. But should there – this is kind of an anomaly or should this bounce back with their largest customer to maybe slightly higher levels?
Josef H. von Rickenbach - Chairman & Chief Executive Officer
Well, as a percent of revenue we're not particularly unhappy with where we are at right now. To have a huge exposure beyond that, of course, if were to get the business obviously we would take it, but we don't particularly anticipate that as a percent of total revenue that, that will go back to where it was.
Steven J. Valiquette - UBS Securities LLC
Okay. I think that helps, maybe we could follow-up offline as well. But, okay. Thanks.
Josef H. von Rickenbach - Chairman & Chief Executive Officer
Okay. You're welcome.
Operator
Thank you. Our next question or comment comes from the line of Todd Van Fleet from First Analysis. Your line is open.
Todd Van Fleet - First Analysis Securities Corp.
Hey, guys. Thanks for hanging on. Just a quick one. A part of the NAT program, I guess is pushing more cost to lower – or pushing more of the cost structure to lower cost geographies. And just the company has talked about that after a very long time, just going back to Jim's days and I think probably even, I don't know, three, four years ago. So I'm just – is there a step function kind of effort going on to – along those lines to make that happen? And if so, could you kind of talk a little bit about what that is, because as I said you've talked about that for some time? Thanks.
Ingo Bank - Chief Financial Officer & Senior Vice President
Yeah, Hi Todd. This is – and this has been the focus and I think we've made great strides in the past to actually do that. I believe I said on a different occasion that we recently authorized the opening of a second shared service center in India, next to the one that we already have over there, which I believe has been indicating that we see more potential. And what Joe was saying that it's an acceleration that's true. So what I would call it a step function? I don't know, but it's simply accelerating the plans we have. And this is not just related to the traditional support functions that one typically considers like HR, finance, IT. This is also true for business support functions that are in the – residing right now in the business, that are now accelerating their plans to move staff to a location where you could do that. I think the step up is now also bit possible given the investments we made in the past. We now have a global ERP infrastructure that simply allows us to automate certain processes and also to handle processes for the company no matter where you are and that we are taking benefit of right now.
Todd Van Fleet - First Analysis Securities Corp.
Thanks.
Josef H. von Rickenbach - Chairman & Chief Executive Officer
Okay. And with that our today's program is concluded. I thank you very much for your interest in PAREXEL and we look forward to updating you after the first quarter's earnings. Thank you very much. Bye-bye.
Operator
Ladies and gentlemen, thank you again for joining us today. This concludes today's conference call. You may now disconnect. The profitability is actually very promising, okay. So of course, you would not deduce that given where they have now been in the startup range. But overall, we expect that we can achieve our goals well in this new environment. And in terms of the size and how much they make up, while oncology has been an important indication and therapeutic area for us for a long time and it would be well over 25% of the total backlog, again buoyed actually by this quarter's new business performance. And overall the backlog would probably be – if I had to give you sort of a guess, I don't have an exact number, but I would say at least a north of a third if not approaching 40%. 
Operator
Thank you. Our next question or comment comes from the line of Steven Valiquette from UBS. Your line is open.
Steven J. Valiquette - UBS Securities LLC
All right. Thanks. Good morning, Joe and Ingo. So I think you as guys mentioned a good news here is that your revenue growth actually your largest customer seems to be witnessing some nice acceleration. But I do have a couple of questions on that largest customer for a minute, anyway.
And I guess, first when we talk about the expected sales acceleration in the CRS segment over the next two to four quarters, just want to confirm whether or not that includes the sales trend that you expect from that largest customer as well. So that's the first question. And then, the second one, I think some investors maybe are still wondering about this, maybe just some close around this topic. Is there any possibility that this third CRO partner brought on by your largest customer may ultimately be hurting your own sales trend lines with that customer or is that not really a factor on what's happening here? Thanks.
Josef H. von Rickenbach - Chairman & Chief Executive Officer
Yeah, hi, Steve. Yeah, so basically – I think I alluded to some of this already before. But just to take the second question upfront. No, we don't expect the third player to hurt us. I think overall outsourcing is going to increase and especially where we're at right now, I wouldn't say that we are sort of the first target anyway.
Overall, we believe that we are in a good place with this client and if you kind of put them into the context of our top five clients, I think they're at a point where they are stabilizing and where we basically can maintain or even grow the backlog that we have with them.
Steven J. Valiquette - UBS Securities LLC
Okay. On that first part though again as far as the sales ramp, I think just your raw sales with that largest customer I think (1:06:27) lowest this quarter it's been since like mid 2012. So just on a raw basis, forget about a percent for a moment. But should there – this is kind of an anomaly or should this bounce back with their largest customer to maybe slightly higher levels?
Josef H. von Rickenbach - Chairman & Chief Executive Officer
Well, as a percent of revenue we're not particularly unhappy with where we are at right now. To have a huge exposure beyond that, of course, if were to get the business obviously we would take it, but we don't particularly anticipate that as a percent of total revenue that, that will go back to where it was.
Steven J. Valiquette - UBS Securities LLC
Okay. I think that helps, maybe we could follow-up offline as well. But, okay. Thanks.
Josef H. von Rickenbach - Chairman & Chief Executive Officer
Okay. You're welcome.
Operator
Thank you. Our next question or comment comes from the line of Todd Van Fleet from First Analysis. Your line is open.
Todd Van Fleet - First Analysis Securities Corp.
Hey, guys. Thanks for hanging on. Just a quick one. A part of the NAT program, I guess is pushing more cost to lower – or pushing more of the cost structure to lower cost geographies. And just the company has talked about that after a very long time, just going back to Jim's days and I think probably even, I don't know, three, four years ago. So I'm just – is there a step function kind of effort going on to – along those lines to make that happen? And if so, could you kind of talk a little bit about what that is, because as I said you've talked about that for some time? Thanks.
Ingo Bank - Chief Financial Officer & Senior Vice President
Yeah, Hi Todd. This is – and this has been the focus and I think we've made great strides in the past to actually do that. I believe I said on a different occasion that we recently authorized the opening of a second shared service center in India, next to the one that we already have over there, which I believe has been indicating that we see more potential. And what Joe was saying that it's an acceleration that's true. So what I would call it a step function? I don't know, but it's simply accelerating the plans we have. And this is not just related to the traditional support functions that one typically considers like HR, finance, IT. This is also true for business support functions that are in the – residing right now in the business, that are now accelerating their plans to move staff to a location where you could do that. I think the step up is now also bit possible given the investments we made in the past. We now have a global ERP infrastructure that simply allows us to automate certain processes and also to handle processes for the company no matter where you are and that we are taking benefit of right now.
Todd Van Fleet - First Analysis Securities Corp.
Thanks.
Josef H. von Rickenbach - Chairman & Chief Executive Officer
Okay. And with that our today's program is concluded. I thank you very much for your interest in PAREXEL and we look forward to updating you after the first quarter's earnings. Thank you very much. Bye-bye.
Operator
Ladies and gentlemen, thank you again for joining us today. This concludes today's conference call. You may now disconnect.