As a private collector for 37 years, Sun Jiazhuo takes pride in his job, not just in his devotion to public record services, but in building up his own family archive.

The 82-year-old resident of Jinan, capital of east China's Shandong Province, started the project by accident in 1983. Later, he came to find pleasure in collecting all the paperwork, much of it bearing precious memories.

In his apartment, Sun's family archives are carefully arranged in a giant four-level bookcase, which takes up most of the space in his study. The archives are held in file boxes, each bearing a tag indicating a specific category.

These archives, ranging from pay slips and food coupons to old photos and family letters, record the great changes his family has experienced over the years, along with China's pursuit of a moderately prosperous society, or "Xiaokang."

In 1979, the Chinese leadership made "Xiaokang" a goal of the country's modernization strategy. The Chinese phrase can be loosely translated as "a comfortable life with some savings," which refers to a condition between subsistence and affluence.

Amid the economic takeoff, the 18th National Congress of the Communist Party of China in 2012 put forward the goal of "completing the building of a moderately prosperous society in all respects" in 2020.

When Sun started working in 1958, he only got paid 26 yuan (about 3.76 U.S. dollars) a month and lived in a small apartment. "However, my monthly salary had reached more than 1,300 yuan when I retired in 1998. This was totally unthinkable in the past," said Sun, who has collected every pay slip showing the pay increases.

Sun and his family also moved to a 144-square-meter apartment in 1998, a giant leap forward for the family.

"The pay kept rising, and in 2018, the monthly retirement pension exceeded 10,000 yuan," he said. Now his pension increases almost on a yearly basis, which is recorded on his bankbook, also part of his family archive.

As for the sharp rise in income and the big improvement in living conditions, the credit goes to the country's reform and opening-up drive, he said.

The past few decades have witnessed the improvement of people's livelihood along with the country's economic boom. The transformation can also be seen in the family's "household appliances" archives.

In the "household appliances" box, at the top of the archives, was the warranty certificate of a ventilating fan, which was used to circulate kitchen air in many homes in China in the last century. In this family, however, the machine has now been replaced with a hi-tech range hood.

According to Sun's archives, over the past two decades, travel has become a new form of recreation for the family. Sun and his wife have travelled a lot, enjoying the best scenery in China, and visiting their son in the United States. Thus, the family archives keep expanding.

Things like recipes written by his wife, letters from children, and greeting cards made by the grandchildren have also been stored in the family archives, capturing warm moments the family spent together.

"Those archives record not only the changes of life, but the evolution of the times. For me, they are helpful in fostering family traditions," said Sun.