Sweden’s National Portrait Gallery is housed in Gripsholm Castle, at Lake Mälaren, about an hour’s drive from Stockholm. The castle, the construction of which was initiated by King Gustav I (Sweden’s own Henry VIII) in the 1530s, is one of the most stately in the country, and its collection of paintings is no less impressive. Among the 5,000 pictures one finds diverse subjects, from sixteenth-century European princes to contemporary worthies such as the Nobel laureate in literature Tomas Tranströmer, Ikea founder Ingvar Kamprad, and Benny Andersson of ABBA.

In the modern section there’s a huge oil painting by Sven Ljungberg (1913-2010). Its title is simple – ‘The Swedish Cabinet in 1974’ – and the picture delivers: a full-figure group portrait of the nineteen members of Olof Palme’s inner circle of social democrat decision-makers. It is a work in typical Ljungberg style: realistic, heavy, not particularly flattering. At least not as far as looks are concerned. When it comes to forcefulness and clout it tells a different story.

That’s also why I think about it every now and then. It provides an important reminder, as ironic as it is valuable.

For a Swedish viewer in the mid-1970s, the picture radiated one thing above all else: power. The people it depicts may not have had quite the might that once belonged to King Gustav, but they were synonymous with political power as citizens at the time knew it.

Aside from a short interlude in the mid-1930s, Sweden had had social democrat governments for 42 continuous years. The party took charge in 1932 and had stayed there. And that did not go only for the party. Some of the individuals in Ljungberg’s painting had been present on the national scene for what must have seemed like an eternity.

Prime Minister Olof Palme became an MP in 1958, and had been a cabinet minister for 11 years in 1974. He was a rookie in comparison to some of his colleagues. Rune B. Johansson, minister of industry, had been in the cabinet since 1957. Eric Holmqvist, minister of defence, joined in 1961: one year before social affairs minister Sven Aspling. Even they were newcomers, though, in comparison to foreign secrerary Sven Andersson, who had been in the cabinet since 1948, and the minister of finance, Gunnar Sträng. The latter joined the cabinet in 1945 and had been in his post for 19 consecutive years in 1974.

A few were younger; up and coming. But almost all those in the portrait were very well anchored in the Social Democratic movement. They held important positions in their constituencies and enjoyed the independence of strong local and regional support. Many had limited formal education, but had acquired an enormous amount of experience through their many years in office and their work in party politics, unions, and other affiliated organisations. And they enjoyed great public trust after having ruled through many years of high growth, rising wages, and the expansion of the social safety net. Rarely, if ever, has so much democratic political capital been represented within one single frame. What’s not there for the eye to see, though, is that they had already started to spend those resources in an astonishing way.

From 1870 to 1970, Sweden’s economy was the fastest growing in the world, together with the Japanese. An increasing tax burden, already evident in the 1950s and 1960s, was broadly accepted since wages were increasing even more – but in the years around 1970 this relationship was broken.

All the successes of social democracy had left the party ideologically intoxicated. Its strategy and policies morphed into something new. They went from piecemeal expansion of the public sector in key areas to radical politicisation of virtually all sectors of society. In economic policy, there was an overconfidence in trying to put the business cycle out of play through excessive public commitments, the so-called bridging policy. There was nothing, it seemed, that could not be achieved through taxes, legislation and ambitious public spending.

Taxes were reaching new heights. From 1970 to 1976, the overall tax burden increased by seven percentage points and payroll taxes rose from 12 to 30 per cent of the wage bill. Beloved children’s book author Astrid Lindgren fell into a famous – and for the Social Democrats devastating – quarrel with minister of finance Gunnar Sträng when she realised she might have to pay 102 per cent in marginal tax. Inflation rose above 10 per cent in 1976, and the same year the unthinkable happened: the Social Democrats lost the election and the centre right took over.

After almost half a century out of office, however, these parties lacked both political capital and self-confidence. The new government avoided controversial decisions and failed to undertake substantial policy changes. In the years 1970 – 1990, the average annual growth of GDP fell to around one per cent, and the situation was further aggravated by a deep structural crisis during the early 1990s.

Eventually, the country managed to return to a more reasonable course after dramatic measures by both centre right and social democratic governments. But it can be said, without exaggeration, that Swedish politics for two decades was dealing with the arrogant mistakes made by the government with the largest political capital that the country has ever seen.

So, from time to time, I go out to Gripsholm Castle to take a good look at Sven Ljungberg’s work of art: to remind myself that self-confidence is good – but humility is even better.