How much sperm should a 70 yr old produce?

Should?: Sperm quality & quantity decreases w/age such that we produce less sperm at age 70 compared to 20yo. How much less is a matter of conjecture. Personal health makes a difference as does genetics. Whether sperm is naturally useable is another issue if suffering from erectile dysfunction although one could consider ART or artificial reproductive techniques. Check out http://goo.gl/uJzyLs for more inf