|
Field
Intervention (Hidden)
|
Before
The field experimental intervention is part of our study in which we mainly collect field data.
Our study starts with a one month period in which we collect for each participating free library baseline data about the number of books in their library, the (second-hand) value of each book and the weekly number of transactions. Second-hand price data in this period are collected from the website of a large Dutch online retailer (Bol.com). On this website, the general public can place all types of second-hand goods for sale. It functions as a platform, as the buyer receives the second-hand goods directly from the seller. We determine the average price of each book by looking at all offerings listed under the book's unique ISBN number or author and title. Books that are registered without an ISBN code are dropped from the sample, unless an author and title are specified. The average price of each second-hand book is determined by taking the average of all price quotes.
This information is used to stratify the libraries into a treatment and control group in week 5. We stratify along the following two dimensions: number of books and the population in the 4digit zipcode in which the library is located. Four subgroups or strata are constructed based on the population and number of books being in the lower or upper 50 percent. We then randomly assign in week 5 of the study half of the libraries within each stratum to the treatment group and the other half to the control group.
Owners of libraries in the treatment group are then send by mail an identical package of 3 books. The three selected book-titles are all novel and best-selling titles. The sales price of this package in stores is about 50 euro. At the time of sending the estimated second-hand price of the package is around 47 euro, around 15 per book. This is higher than the average second-hand book price in the collection of books as reported by the library owners in the first week of the study (which was around 9.5 euro). Hence, when these books appear in the libraries, they will in most libraries be among the most valuable books. The treatment hence positively shocks the quality of local libraries as measured by second-hand market value.
Owners are asked to put these books in their library in the sixth week of the study. Library owners in the control group receive the same package of books but they receive them in August or September 2019 such that in the intermediate period, these libraries serve as the control group, showing how transactions evolve without the positive supply shock mentioned above.
Of course, the value of the package of books is likely to change over time. These titles are just on the market when the libraries in the treatment group receive them but considerably longer when the libraries in the control group receive them. To account for this difference in value (which we expect to decrease over time), the rating of the individual book value is repeated in every week of the study, using the current second-hand market value as listed on Bol.com. We not only do this for the package of three books but for all books present in the libraries. In this way, we correct for the common value depreciation of books. (Even if no transactions take place in a library, the value of its collection is likely to decrease.)
We have three hypotheses regarding the field experimental intervention.
1) The three books (our treatment) disappear faster from the library compared to books in the control group.
2) The three books (our treatment) are brought back to the library less often compared to books in the control group.
3) In the period post treatment, books that newly enter libraries in the treatment group are taken out of the library faster than books that newly enter libraries in the control group. This measures the multiplier effect from our intervention. In the test of this third hypothesis, we exclude from the analysis the three books from our treatment package that were sent to the libraries in the treatment group.
|
After
The field experimental intervention is part of our study in which we mainly collect field data.
Our study starts with a one month period in which we collect for each participating free library baseline data about the number of books in their library, the (second-hand) value of each book and the weekly number of transactions. Second-hand price data in this period are collected from the website of a large Dutch online retailer (Bol.com). On this website, the general public can place all types of second-hand goods for sale. It functions as a platform, as the buyer receives the second-hand goods directly from the seller. We determine the average price of each book by looking at all offerings listed under the book's unique ISBN number or author and title. Books that are registered without an ISBN code are dropped from the sample, unless an author and title are specified. The average price of each second-hand book is determined by taking the average of all price quotes.
This information is used to stratify the libraries into a treatment and control group in week 5. We stratify along the following two dimensions: number of books and the population in the 4digit zipcode in which the library is located. Four subgroups or strata are constructed based on the population and number of books being in the lower or upper 50 percent. We then randomly assign in week 5 of the study half of the libraries within each stratum to the treatment group and the other half to the control group.
Owners of libraries in the treatment group are then send by mail an identical package of 3 books. The three selected book-titles are all novel and best-selling titles. The sales price of this package in stores is about 50 euro. At the time of sending the estimated second-hand price of the package is around 47 euro, around 15 per book. This is higher than the average second-hand book price in the collection of books as reported by the library owners in the first week of the study (which was around 9.5 euro). Hence, when these books appear in the libraries, they will in most libraries be among the most valuable books. The treatment hence positively shocks the quality of local libraries as measured by second-hand market value.
Owners are asked to put these books in their library in the sixth week of the study. Library owners in the control group receive the same package of books but they receive them in August or September 2019 such that in the intermediate period, these libraries serve as the control group, showing how transactions evolve without the positive supply shock mentioned above.
Of course, the value of the package of books is likely to change over time. These titles are just on the market when the libraries in the treatment group receive them but considerably longer when the libraries in the control group receive them. To account for this difference in value (which we expect to decrease over time), the rating of the individual book value is repeated in every week of the study, using the current second-hand market value as listed on Bol.com. We not only do this for the package of three books but for all books present in the libraries. In this way, we correct for the common value depreciation of books. (Even if no transactions take place in a library, the value of its collection is likely to decrease.) The books that are not listed on Bol.com will be searched for individually on Boekwinkeltjes.nl, a website specialized in second-hand book sales.
We have three hypotheses regarding the field experimental intervention.
1) The three books (our treatment) disappear faster from the library compared to books in the control group.
2) The three books (our treatment) are brought back to the library less often compared to books in the control group.
3) In the period post treatment, books that newly enter libraries in the treatment group are taken out of the library faster than books that newly enter libraries in the control group. This measures the multiplier effect from our intervention. In the test of this third hypothesis, we exclude from the analysis the three books from our treatment package that were sent to the libraries in the treatment group.
|