In some countries deposit arrangements may be a mixture of legal and voluntary deposit. Such hybrid arrangements may be a pragmatic response by national bibliographic agencies to the restricted scope of legal deposit. Selective voluntary deposit schemes may also arise from long standing agreements between the national bibliographic agency and a specific sector, such as the recording industry.
Voluntary schemes may be temporary, as when governments and national bibliographic agencies trial the extension of deposit to new categories of material through voluntary arrangements. The risk is that such temporary schemes may not ultimately lead to legal deposit. National bibliographic agencies should therefore monitor the relative effectiveness of such schemes compared to formal measures for other classes of material in order to support the case for extension of legal deposit.