"So, they've increased their revenue, in part at least, through...

"So, they've increased their revenue, in part at least, through acquisitions and introduced the improvements you referred to above, yet they've not enjoyed any efficiency gains through this period according to this graph."

Graph? I can only see a table which shows Revenue and Expenses as a % of costs. Neither of these measurements are related to Efficiency.
Efficiency would be measured by;
1. Number of tests and results per dollar spent by the Gov. or individual patient.
and
2. "Turnaround time" - the speed at which the aforementioned results take to be in front of the Medical Practitioner or Hospital Doctor either on sheets of paper or on computer files.

I can assure you that the above measurements have improved in each of the last 40 years since I joined the industry.

The company revenue is almost entirely dependent on the amount the Govt. is prepared to pay or refund for the tests performed.

Anyone who has had testing done by labs or X-Ray clinics is aware that the cost of the tests is rarely refunded in full. Some costs are not refunded at all. Even those fully "insured" do not get full refunds most of the time. I had an Echocardiogram done recently and my health insurer would not refund ANY of the $240 cost.