Statistics about my collection of season programs and opera performances

I have made a statistical study of my collection of monthly, bimonthly and yearly program books and magazines of opera houses and festivals, as well as of opera performances. Since I have started my collection, I also have compiled a calendar of opera performances with the following datas for each performance :

date, composer, opera title, conductor, director, performance location, city

Since the early 1990s, I have collected 7616 paper documents mostly from Europe and North America including 567 magazines. I have also downloaded 840 PDF documents of the same kind. Some of the PDF documents are copies of original paper documents I have.

Here is the graph for my collection of magazines (graphs might be enlarged by clicking on them) :

Here is the graph showing the growth of my collection of monthly and yearly programs :

The calendar of opera performances I have compiled contains 164585 performances, starting in October 1987. Here is a graph showing the number of performances for each season. A season starts on September 1st and ends on August 31st.

I havn't received all programs for the 2014-2015 seasons, so this number will grow soon.

Thanks to my calendar, I can also know which composers and what operas have been the most performed in the last 25 years.

The 25 composers with more than 1000 performances in that period (40 performances minimum every year in average) are (in order of decreasing number of performances) : Giuseppe Verdi, Wolfgang Amadeus Mozart, Giacomo Puccini, Richard Wagner, Gioachino Rossini, Richard Strauss, Gaetano Donizetti, Georges Bizet, Jacques Offenbach, Johann Strauß, Georg Friedrich Haendel, Benjamin Britten, Leos Janacek, Franz Lehar, Pyotr Ilyich Tchaikovsky, Jules Massenet, Engelbert Humperdinck, Vincenzo Bellini, Ludwig van Beethoven, Charles Gounod, Christoph Willibald Gluck, Claudio Monteverdi, Ruggero Leoncavallo, Pietro Mascagni and Modest Mussorgsky.

Here is a graph showing the number of performances for each composer every year :

We can notice the peaks of Verdi performances in 2001 and Wagner in 2013.

In my calendar, I have 2360 different operas composed by 1057 composers. The 10 most performed operas in the last 25 years are (in order of decreasing number of performances) : Mozart's Die Zauberflöte, Verdi's La Traviata, Puccini's La Bohème, Bizet's Carmen, Mozart's Le Nozze di Figaro, Puccini's Tosca, Mozart's Don Giovanni, Puccini's Madama Butterfly, Rossini's Il Barbiere di Siviglia and Verdi's Rigoletto.

Here is the graph :

The 10 following operas are : Mozart's Cosi fan tutte, Johann Strauß's Die Fledermaus, Verdi's Aida, Humperdinck's Hänsel und Gretel, Donizetti's L'elisir d'amore, Mozart's Die Entführung aus dem Serail, Wagner's Der fliegende Holländer, Lehar's Die lustige Witwe, Puccini's Turandot and Offenbach's Les Contes d'Hoffmann.