Table:
|  |  | Years Ended December 31, |  |
| --- | --- | --- | --- |
| Customer Type | 2017 | 2018 | 2019 |
|  | % | % | % |
| Fabless design companies | 91.0 | 92.4 | 91.3 |
| Integrated device manufacturers | 9.0 | 7.6 | 8.7 |
| Total | 100.0 | 100.0 | 100.0 |
Paragraphs:
We believe our success in attracting these end customers is a direct result of our commitment to high quality service and our intense focus on customer needs and performance. As an independent semiconductor foundry, most of our operating revenue is generated by our sales of wafers. The following table presented the percentages of our wafer sales by types of customers for the years ended December 31, 2017, 2018 and 2019.
We focus on providing a high level of customer service in order to attract customers and maintain their ongoing loyalty. Our culture emphasizes responsiveness to customer needs with a focus on flexibility, speed and accuracy throughout our manufacturing and delivery processes. Our customer oriented approach is especially evident in two types of services: customer design development services and manufacturing services.
For example, in 2013, we expand our regional business by opening our UMC Korea office, in order to provide local support to our customers in Korea, and shorten time-to-market for our Korea-based customers designing and manufacturing on UMC process technologies. We believe that our large production capacity and advanced process technology enable us to provide better customer service than many other foundries through shorter turn-around time, greater manufacturing flexibility and higher manufacturing yields.
Question:
What is the increase / (decrease) in the Integrated device manufacturers from 2017 to 2018?
Answer: 7.6% - 9.0% = -1.4