The phrase "about which customers" is correct and usable in written English.
It can be used when referring to specific customers in a discussion or inquiry, often in a formal context.
Example: "We need to gather more information about which customers have shown interest in our new product line."
Alternatives: "regarding which customers" or "concerning which customers".
During the fallow period after the boom, online brokerages have grown smarter about which customers are the most profitable, and are offering different levels of service and price.
He has one staff member to fill out employee forms, handle his payroll, manage his e-mail list and make all-important choices about which customers will get holiday gifts.
In others, it means actually using the mountains of data that e-tailers have said all along would help speed their earnings growth -- by allowing them to make better decisions about which customers are the most profitable, for instance.
Another frustration: China has little information about which customers are mostly likely to pay their bills.
However, lenders said they would still continue to be very fussy about which customers they would chose to lend money.
The UK's data regulator, the Information Commissioner's Office, is advising the parties about the collection of data about which customers receive alerts.
Amazon did not respond to a request seeking further information about which customer was using its service to disperse the spyware.
The gift cards have been trickling out into the public for at least a few days now, but nothing solid has turned up about exactly which customers are able to benefit.
In this case, social media interactions serve as a source of information from which customers learn about products and services and form their attitude regarding them.
Nathaniel L. Benson, president and chief executive of Lab 21, said the genetic variations that are detected provide information about which ingredients are best for which customers.
Much of this software has also proven useful at SAS, said Mr. Goodnight".We use our own software to find new customers and to predict which customers we're about to lose," he said.
