Opinion polls can be fickle and hard to read - but for the NHS one carries a fair amount of clout.
The British Social Attitudes Survey has a track record going back to 1983 and so is a fascinating guide to long-term trends.
The latest publication suggests a significant downturn in public satisfaction with the NHS, which had been holding up in recent years.
So does this herald a game-changing trend in the debate over the NHS, with important implications for the government and health service leaders?
Is the quality of care now affecting the public perceptions of hospitals and GP surgeries?
The squeeze on NHS services, with patient demand rising more rapidly than health budgets, has been clear since the coalition government's deficit reduction plan took hold after 2010.
But overall public satisfaction with the NHS remained relatively high, at or above 60%.
This is based on the question: "How satisfied or dissatisfied would you say you are with the way in which the NHS runs nowadays?"
The polling for 2017, however, records a six-percentage-point drop in satisfaction, to 57%, and a seven-percentage-point increase in those saying they are dissatisfied, to 29%, the highest in a decade.
The gap between the two has narrowed to the lowest since 2007.
The survey, based on interviews with 3,000 adults in England, Scotland and Wales, was carried out before the start of the 2017-18 winter so it seems unlikely to have been swayed by negative media headlines, although the NHS was prominently in the news for much of the year.
Back in the mid-1990s, there were more dissatisfied respondents than those saying they were content with the NHS.
In the early years of the Labour government, the two views were more or less level.
Then, satisfaction began to pull ahead of dissatisfaction, coinciding with spending increases.
Reasons for unhappiness
The reasons for people saying they are unhappy with the NHS overall are intriguing.
The analysis of the data by the Nuffield Trust and King's Fund think tanks examines responses to questions going back to 2015.
The number agreeing that money is wasted in the NHS has fallen, whereas the number who feel the government in whichever part of the UK they live is not spending enough on the NHS has risen significantly.
There was an increase, too, in those who believe there are not enough staff.
There was, though, a slight fall in those blaming long waits for GP or hospital appointments.
The fact that more people are highlighting NHS funding as an issue will be a concern for Whitehall and the devolved administrations.
The news comes soon after the regulator NHS Improvement reported that trusts in England had run up deficits of nearly £1.3bn in the first nine months of the current financial year, £365m more than planned.
There is increasing speculation that the Department of Health and Social Care, covering England, is struggling to balance the books this year even after more funding was allocated in the Budget.
The Royal College of Psychiatrists recently reported that the income of mental health trusts in England had fallen since 2011, after taking account of inflation.
This was mirrored in government data from Scotland, Wales and Northern Ireland.
The college said in some areas services were being cut because of funding even as demand was "soaring".
The Department of Health and Social Care pointed to planned funding increases over the next two years.
An official said: "Just last year the NHS was rated as the best and safest health system in the world by independent experts, and as this report itself points out, the majority of patients are satisfied with the NHS.
"Moreover, the number of staff who would recommend the care their organisation provides to their own family has never been higher."
But Prof John Appleby, of the Nuffield Trust, said that "the tide has started to turn" and that the trends highlighted in the report suggested that "the public are worried about the NHS".
More recent polling work reveals continuing public unease.
An Ipsos Mori report based on fieldwork in January this year recorded "a rise in concern" after a 10-percentage-point increase since December in the proportion who considered the NHS to be a big issue for the country, to 55%.
Apart from a peak of 61% in May 2017, that was said to be the highest score since 2002.
The NHS will generate many more headlines in 2018, with the 70th anniversary commemorations approaching.
Public views on services and funding will need to be watched closely by politicians and NHS leaders.