public function stats() {
		$keys = [];
		$keys['unused_valid'] = $this->find('count', ['conditions' => [$this->getAlias() . '.used' => 0, $this->getAlias() . '.created >=' => date(FORMAT_DB_DATETIME, time() - $this->validity)]]);
		$keys['used_valid'] = $this->find('count', ['conditions' => [$this->getAlias() . '.used' => 1, $this->getAlias() . '.created >=' => date(FORMAT_DB_DATETIME, time() - $this->validity)]]);

		$keys['unused_invalid'] = $this->find('count', ['conditions' => [$this->getAlias() . '.used' => 0, $this->getAlias() . '.created <' => date(FORMAT_DB_DATETIME, time() - $this->validity)]]);
		$keys['used_invalid'] = $this->find('count', ['conditions' => [$this->getAlias() . '.used' => 1, $this->getAlias() . '.created <' => date(FORMAT_DB_DATETIME, time() - $this->validity)]]);

		$types = $this->find('all', ['conditions' => [], 'fields' => ['DISTINCT type']])->toArray();
		$keys['types'] = !empty($types) ? Hash::extract($types, '{n}.type') : [];
		return $keys;
	}