Pope Leo XIV’s first encyclical, Magnifica humanitas, will be released on May 25, 2026. He officially signed it on May 15, exactly 135 years after the publication of another famous encyclical, Rerum novarum (“Of New Things”), signed by Leo XIII.
This direct connection, part of the development of Catholic social teaching, highlights the importance the Church places on these “encyclical letters.” With the help of infographics, here’s an overview of how popes' use of these texts has shifted dramatically since Leo XIII.
Since Benedict XIV (1740–1758), pontiffs have used the specific format of the encyclical to publish a multitude of teaching texts on theological, ecclesial, and socio-political themes. Derived from the Greek enkuklios, meaning circular, and the Latin litterae encyclicae, an encyclical was originally a “circular letter” sent by the pope to the world's bishops, or a portion of them. Through them, it also reached the clergy and the faithful, and sometimes even “all people of good will.”
These papal texts have teaching value. They occasionally contain warnings and, more rarely, condemnations. However, an encyclical doesn't promulgate new dogmas. Instead, it offers an analysis of doctrine, proposes remedies, and honors exemplary figures, such as the Virgin Mary, or, as in Pope Francis' last encyclical, the Sacred Heart.
The prolific era of Leo XIII
Leo XIII (1878–1903), whose name the current pope has taken, remains the undisputed champion of encyclicals. He wrote an astonishing 86 of them during his 25-year pontificate. (He did have the fourth-longest reign in pontifical history, after only St. Peter, Pius IX in the mid 1800s, and John Paul II.)
On the other end of the spectrum, John Paul I naturally ranks last, having published no encyclicals during his 33-day pontificate in 1978. The theologian-pope Benedict XVI (2005–2013) published just three encyclicals during his eight years on the Chair of Peter.
A post-Vatican II decline
Relative to the length of his pontificate, Leo XIII remains the most prolific pope. He averaged nearly three and a half encyclicals a year, releasing eight in 1888 alone. Pius XII follows him, authoring more than two per year, followed by John XXIII (1958–1963), Pius XI, and Benedict XV (1914–1922), who each averaged just under two a year.
Conversely, Pope Francis wrote about one encyclical every three years. That number is notably low given that his 2013 encyclical, Lumen fidei (“The Light of Faith”), was largely drafted by his predecessor.
Broadly speaking, the Church saw a decline in the use of encyclicals following the Second Vatican Council. Paul VI, St. John Paul II, and Benedict XVI all published roughly one encyclical every two years. This marks a sharp drop from the pontificates of the first half of the 20th century, when a year without an encyclical was rare.
Out of the 220 encyclicals published from Leo XIII to the present day, fewer than 10% have been released since St. John Paul II's election 48 years ago.
Diversifying papal documents
This decline stems primarily from the diversification of document formats used by popes throughout the 20th century, particularly the rise of apostolic letters and apostolic exhortations. An apostolic exhortation is a magisterial text similar to an encyclical, as both carry universal weight, but an encyclical invests the text with greater solemnity. An apostolic letter, meanwhile, often addresses a specific category of the faithful or a particular event, carrying less formal solemnity.
While highly productive with encyclicals, Leo XIII and Pius XI never published an apostolic exhortation. In general, this format remained relatively rare until the pontificate of Paul VI (1963–1978). It then became standard practice, with an average of about one every two years under Benedict XVI and Francis. After Vatican II, the publication of an apostolic exhortation has often been linked to a synod—a major thematic meeting—held in Rome. Many apostolic exhortations are named, precisely, post-synodal apostolic exhortations.
Shifts from local to global themes
Changing themes also explain this evolution in frequency. In pre-Vatican II pontificates, many encyclicals targeted the specific Church of a single nation. This was the case for Leo XIII’s 1892 French-language encyclical Au milieu des sollicitudes (“On the Church and State in France”), which marked the beginning of the Catholic Church’s reconciliation with the French Republic. Similarly, in his 1937 German-language encyclical Mit brennender Sorge (“With Burning Anxiety”), Pius XI condemned Nazism.
In recent decades, popes have stopped addressing encyclicals to local Churches, preferring apostolic letters or exhortations instead, though even those remain rare. Regional situations are now handled through synods, resulting in apostolic exhortations such as Querida Amazonia (“Beloved Amazon”), published in 2020 a few months after the synod on the Amazon basin.
When addressing a specific nation, recent popes have opted for simpler formats. Benedict XVI sent a simple letter — not an apostolic one — to Chinese Catholics in 2007, and Francis did the same for German Catholics in 2019.
Modern pontiffs also favor exhortations or apostolic letters for commemorations, such as the centennial anniversaries of great saints or major historical events. By contrast, their predecessors routinely signed encyclicals for these occasions. The most recent example's the apostolic letter In unitate fidei (“In the Unity of Faith”), published by Leo XIV on November 23, 2025, to mark the 1,700th anniversary of the Council of Nicaea.
Longer texts and slower writing
In the 20th century, historical circumstances heavily shaped the use of encyclicals. Twenty-five encyclicals, spanning from Leo XIII to Paul VI, focused on war and peace-building during and after the two World Wars. Under John XXIII and Paul VI, the two popes of Vatican II, the Church underwent its aggiornamento, showing a wide variety of themes that reflected that important era's dynamic energy.
Beyond localized and commemorative encyclicals, a significant portion (13%) focused on devotions. Interestingly, Catholic social teaching has been a relatively rare theme since Leo XIII, accounting for less than 7% of all encyclicals, though it has spiked significantly since St. John Paul II (29%).
The shrinking number of encyclicals also comes down to a concrete evolution of this format: they've grown much longer. Francis’ encyclicals, for instance, are nearly 10 times longer than those of Leo XIII. One cause for this is the fact that modern popes no longer use encyclicals for commemorations, anniversaries, and other occasions requiring no more than brief texts.
The longest encyclical, Evangelium vitae (“The Gospel of Life”), with more than 45,000 words, was published by St. John Paul II in 1995 to address the “inviolability of human life.” The shortest, Quod votis (348 words), was released by Leo XIII in 1902 to permit the Austro-Hungarian Empire to establish a pontifical university.
Because these texts are so much thicker, popes naturally take longer to write them. Leo XIII, Pius X, and Benedict XV waited only two months to publish their first encyclicals. In contrast, Leo XIV took 13 months, and Paul VI waited 14 months.
