My answer as of 2015
In 2008, 4% of U.S. physicians reported having an extensive, fully functional electronic-records system, and 13% reported having a basic system, according to the New England Journal of Medicine, see Common Examples of Healthcare IT Failure (Drexel University).
By May 2013, approximately 90% of health care facilities had implemented an electronic health record (EHR) system although only 56% of long-term care facilities had done so, see Long-term care facilities lag behind on EHR adoption.
As for physicians, CDC Releases Report on Physician EHR Adoption in 2014 indicated an EHR adoption rate of 78%. Here is some data about physicians' usage of digital records and technology via Survey shows EHR skepticism increasing among U.S. doctors published 15 April 2015.
The number of U.S. doctors who routinely use digital tools, such as secure email, for communicating with patients is 30% now versus 13% in 2012.
The five IT capabilities that U.S. doctors use the most are:
- entering patient notes electronically (82%);
- prescribing drugs electronically (72%);
- receiving clinical results directly into a patient’s EMR (65%);
- using electronic administration tools (63%);
- sending e-order requests to labs (62%).
I don't know the composition of the complementary data. It depends on the number of N/A or "didn't know" or "didn't respond to that question" versus "I use paper" responses.
A note about terminology
An EMR is an Electronic Medical Record. An EHR (Electronic Health Record) system consists of either EMRs or EHRs, i.e. they are used interchangeably. I don't often see "EMR systems". I'm unsure why "EHR systems" is the more common term. Often, context is necessary to determine whether "EHR" refers to an EHR system or an EHR.
