I don't know where and if these data exist at the european level, but I may contribute with data about some cases in France.  If everyone contributes and ask to his colleagues in this area, it could be a nice product of collaborative science !

 Hi Biron

Here some data from 2016

Affiliated federations of the Office International du Coin de Terre et des Jardins Familiaux a.s.b.l.

  Country                                              Member families                                Hectares

Federation:

         of Austria                                       40.126                                             824

        of Belgium                                      35.000                                             150

       of Denmark                                     40.000                                          1.200

        of Finland                                         3.900                                             270

        of France                                          25.000                                           500

       of Germany                                     940.000                                     45.000  

        of Great Britain                              115.000                                      10.000

        of Japan                                              1.003                                                 5,9

         of Luxembourg                               20.350                                          1.500

         of the Netherlands                          28.000                                          1.000

         of Norway                                           3.000                                                56

         of Sweden                                        24.100                                               700

          of Switzerland                                  22.600                                             580

                                               __________                                         __________

                                                                  1.298.079                                      61.785,9

 No more members       

Federation of Poland                                  1.100.000                         43.522,67

                  of Slovakia                                      127.642                            5.700

Remarks:

Austria:        390 associations  majority in Vienna

Belgium:      240 associations in Flandria; 50 associations in Wallonia

Denmark:      410 associations

Germany:      15.000 associations

Finland:              32 associations. They represent 53% of the local associations and                          64% of the  Finnish allotment gardeners

France:          279 local associations, committees or sites

Great-Britain: 2.500 associations, 247 local authorities, 1.335 individuals, 951 life

                       member  and 33 schools. The federation represents over a third of the

                       English  allotment gardeners

Luxembourg: 115 local associations.20% of the members have a plot in one of the 25 allotment sites.80% have a private garden

The Netherlands:215 associations

Norway:          16 associations mainly Oslo and Stavanger

Sweden:           230 associations from 640 associations representing 24.100                                       member from 51.000 gardeners

Switzerland:   290 associations in the German and French part of Switzerland

We issued last year a new information brochure. If you send me your email address I'll be pleased to send it to you

Best regards

Malou WEIRICH

Hi Byron

you find a lot of Information in this books:

Simon Bell; Rundrid Fox-Kämper et al. (Hg.) 2016: Urban Allotment Gardens in Europe

: COST Action 1201. London: Routledge.

Frank Lohberg, Lilli Licka et al (Hg) 2016: Urban Agriculture Europe (COST Action xx?)

Jovis Verlag GmbH Berlin

Thank you Yvonne

You find a lot of Information in this books:

Simon Bell; Rundrid Fox-Kämper et al. (Hg.) 2016: Urban Allotment Gardens in Europe

: COST Action 1201. London: Routledge.