diff --git a/app/assets/javascripts/controllers/admin/events.coffee b/app/assets/javascripts/controllers/admin/events.coffee
index 93e080fb6..f15fc5606 100644
--- a/app/assets/javascripts/controllers/admin/events.coffee
+++ b/app/assets/javascripts/controllers/admin/events.coffee
@@ -194,11 +194,14 @@ Application.Controllers.controller "AdminEventsController", ["$scope", "$state",
     if model == 'category' and getModel(model)[1].length == 1
       growl.error(_t('at_least_one_category_is_required_unable_to_delete_the_last_one'))
       return false
+    if getModel(model)[1][index].related_to > 0
+      growl.error(_t('unable_to_delete_ELEMENT_already_in_use_NUMBER_times', {ELEMENT:model, NUMBER:getModel(model)[1][index].related_to}, "messageformat"))
+      return false
     dialogs.confirm
       resolve:
         object: ->
           title: _t('confirmation_required')
-          msg: _t('do_you_really_want_to_delete_this_ELEMENT_used_NUMBER_times', {ELEMENT:model, NUMBER:getModel(model)[1][index].related_to}, "messageformat")
+          msg: _t('do_you_really_want_to_delete_this_ELEMENT', {ELEMENT:model}, "messageformat")
     , -> # delete confirmed
       getModel(model)[0].delete getModel(model)[1][index]
       getModel(model)[1].splice(index, 1)
diff --git a/app/models/age_range.rb b/app/models/age_range.rb
index 7f0142cc5..0bc247d8c 100644
--- a/app/models/age_range.rb
+++ b/app/models/age_range.rb
@@ -1,3 +1,6 @@
 class AgeRange < ActiveRecord::Base
+  extend FriendlyId
+  friendly_id :name, use: :slugged
+
   has_many :events, dependent: :nullify
 end
diff --git a/app/models/category.rb b/app/models/category.rb
index e812aae3b..98328b9d0 100644
--- a/app/models/category.rb
+++ b/app/models/category.rb
@@ -1,8 +1,33 @@
 class Category < ActiveRecord::Base
+  extend FriendlyId
+  friendly_id :name, use: :slugged
+
   has_and_belongs_to_many :events, join_table: :events_categories, dependent: :destroy
 
+  after_create :create_statistic_subtype
+  after_update :update_statistic_subtype, if: :name_changed?
+  after_destroy :remove_statistic_subtype
+
+
+  def create_statistic_subtype
+    index = StatisticIndex.where(es_type_key: 'event')
+    StatisticSubType.create!({statistic_types: index.first.statistic_types, key: self.slug, label: self.name})
+  end
+
+  def update_statistic_subtype
+    index = StatisticIndex.where(es_type_key: 'event')
+    subtype = StatisticSubType.joins(statistic_type_sub_types: :statistic_type).where(key: self.slug, statistic_types: { statistic_index_id: index.first.id }).first
+    subtype.label = self.name
+    subtype.save!
+  end
+
+  def remove_statistic_subtype
+    subtype = StatisticSubType.where(key: self.slug).first
+    subtype.destroy!
+  end
+
   def safe_destroy
-    if count > 1
+    if Category.count > 1 && self.events.count == 0
       destroy
     else
       false
diff --git a/app/models/event_theme.rb b/app/models/event_theme.rb
index 86bc0fb3c..4b39a5cef 100644
--- a/app/models/event_theme.rb
+++ b/app/models/event_theme.rb
@@ -1,3 +1,6 @@
 class EventTheme < ActiveRecord::Base
+  extend FriendlyId
+  friendly_id :name, use: :slugged
+
   has_and_belongs_to_many :events, join_table: :events_event_themes, dependent: :destroy
 end
diff --git a/config/locales/app.admin.en.yml b/config/locales/app.admin.en.yml
index b514ade85..d4cc98563 100644
--- a/config/locales/app.admin.en.yml
+++ b/config/locales/app.admin.en.yml
@@ -84,7 +84,8 @@ en:
         add_a_theme: "Add a theme"
         age_ranges: "Age ranges"
         add_a_range: "Add a range"
-        do_you_really_want_to_delete_this_ELEMENT_used_NUMBER_times: "Do you really want to delete this {ELEMENT, select, category{category} theme{theme} age_range{age range} other{element}}? {NUMBER, plural, =0{It is not currently associated with any events} one{Currently, it is associated with only one event} other{Currently, it is associated with {NUMBER} events}}."  # messageFormat interpolation
+        do_you_really_want_to_delete_this_ELEMENT: "Do you really want to delete this {ELEMENT, select, category{category} theme{theme} age_range{age range} other{element}}?"  # messageFormat interpolation
+        unable_to_delete_ELEMENT_already_in_use_NUMBER_times: "Unable to delete this {ELEMENT, select, category{category} theme{theme} age_range{age range} other{element}} because it is already associated with {NUMBER, plural, =0{no events} one{one event} other{{NUMBER} events}}."  # messageFormat interpolation
         at_least_one_category_is_required_unable_to_delete_the_last_one: "At least one category is required. Unable to delete the last one."
 
       events_new:
diff --git a/config/locales/app.admin.fr.yml b/config/locales/app.admin.fr.yml
index 974ac48f2..bda0fa36a 100644
--- a/config/locales/app.admin.fr.yml
+++ b/config/locales/app.admin.fr.yml
@@ -84,7 +84,8 @@ fr:
         add_a_theme: "Ajouter une thématique"
         age_ranges: "Tranches d'âge"
         add_a_range: "Ajouter une tranche"
-        do_you_really_want_to_delete_this_ELEMENT_used_NUMBER_times: "Voulez-vous vraiment supprimer cette {ELEMENT, select, category{catégorie} theme{thématique} age_range{tranche d'âge} other{élément}} ? {NUMBER, plural, =0{Elle n'est actuellement associée à aucun évènement} one{Elle est actuellement associée à un seul évènement} other{Elle est actuellement associée à {NUMBER} évènements}}."  # messageFormat interpolation
+        do_you_really_want_to_delete_this_ELEMENT: "Voulez-vous vraiment supprimer cette {ELEMENT, select, category{catégorie} theme{thématique} age_range{tranche d'âge} other{élément}} ?"  # messageFormat interpolation
+        unable_to_delete_ELEMENT_already_in_use_NUMBER_times: "Impossible de supprimer cette {ELEMENT, select, category{catégorie} theme{thématique} age_range{tranche d'âge} other{élément}} car elle est actuellement associée à {NUMBER, plural, =0{aucun évènement} one{un évènement} other{{NUMBER} évènements}}."  # messageFormat interpolation
         at_least_one_category_is_required_unable_to_delete_the_last_one: "Au moins une catégorie est requise. Impossible de supprimer la dernière."
 
       events_new:
diff --git a/db/migrate/20160630083438_add_slug_to_categories.rb b/db/migrate/20160630083438_add_slug_to_categories.rb
new file mode 100644
index 000000000..0914484ab
--- /dev/null
+++ b/db/migrate/20160630083438_add_slug_to_categories.rb
@@ -0,0 +1,6 @@
+class AddSlugToCategories < ActiveRecord::Migration
+  def change
+    add_column :categories, :slug, :string
+    add_index :categories, :slug, unique: true
+  end
+end
diff --git a/db/migrate/20160630083556_add_slug_to_age_range.rb b/db/migrate/20160630083556_add_slug_to_age_range.rb
new file mode 100644
index 000000000..1dcff4ee7
--- /dev/null
+++ b/db/migrate/20160630083556_add_slug_to_age_range.rb
@@ -0,0 +1,6 @@
+class AddSlugToAgeRange < ActiveRecord::Migration
+  def change
+    add_column :age_ranges, :slug, :string
+    add_index :age_ranges, :slug, unique: true
+  end
+end
diff --git a/db/migrate/20160630083759_add_slug_to_event_theme.rb b/db/migrate/20160630083759_add_slug_to_event_theme.rb
new file mode 100644
index 000000000..6c608add6
--- /dev/null
+++ b/db/migrate/20160630083759_add_slug_to_event_theme.rb
@@ -0,0 +1,6 @@
+class AddSlugToEventTheme < ActiveRecord::Migration
+  def change
+    add_column :event_themes, :slug, :string
+    add_index :event_themes, :slug, unique: true
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index f574480e5..4a3f17e06 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20160629091649) do
+ActiveRecord::Schema.define(version: 20160630083759) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -48,8 +48,11 @@ ActiveRecord::Schema.define(version: 20160629091649) do
     t.string   "name"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.string   "slug"
   end
 
+  add_index "age_ranges", ["slug"], name: "index_age_ranges_on_slug", unique: true, using: :btree
+
   create_table "assets", force: :cascade do |t|
     t.integer  "viewable_id"
     t.string   "viewable_type", limit: 255
@@ -92,8 +95,11 @@ ActiveRecord::Schema.define(version: 20160629091649) do
     t.string   "name",       limit: 255
     t.datetime "created_at"
     t.datetime "updated_at"
+    t.string   "slug"
   end
 
+  add_index "categories", ["slug"], name: "index_categories_on_slug", unique: true, using: :btree
+
   create_table "components", force: :cascade do |t|
     t.string "name", limit: 255, null: false
   end
@@ -124,8 +130,11 @@ ActiveRecord::Schema.define(version: 20160629091649) do
     t.string   "name"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.string   "slug"
   end
 
+  add_index "event_themes", ["slug"], name: "index_event_themes_on_slug", unique: true, using: :btree
+
   create_table "events", force: :cascade do |t|
     t.string   "title",           limit: 255
     t.text     "description"