private void economicUpdate() {
    if (base().credits() < 500) base().incCredits(1000) ;
    
    final Batch <Venue> sampled = new Batch <Venue> () ;
    final World world = world() ;
    final Tile t = world.tileAt(world.size / 2, world.size / 2) ;
    world.presences.sampleFromKey(t, world, 100, sampled, Venue.class) ;
    
    for (Venue v : sampled) {
      final Service services[] = v.services() ;
      if (services != null) for (Service s : services) {
        if (v.stocks.amountOf(s) < 5) v.stocks.bumpItem(s, 10) ;
      }
      for (Actor a : v.personnel.residents()) {
        if (a.gear.credits() < 500) a.gear.incCredits(1000) ;
      }
    }
  }