Sherry,
Yes, different seeds have different percents. Seed saved no matter how perfectly will not have all viable seeds. Some plants have a normally high rate as is with most veggies, and some are low. This is especially true with some flower seeds.
Tomato seeds need to be 75%. I make sure mine are above 85%. I prefer 90 or above. One time, I had Cherokee Green at 75% and offered them as an extra bonus upon request. Or one time I had a pepper variety that only had a 60% germ rate, Federal rate is 55% (I think that is really low, but peppers are sometimes finickier than other seed,) so I gave a lot of extra seed with instructions to over sow to compensate.
Kath,
No, seed does not have to be produced the year it is sold. Most companies are reputable. There's a few bad ones out there. Reimer's comes to mind with many complaints of low/no germination. They have tons of complaints on The Garden Watchdog. The recommended list of vendors here is great, but it is limited to companies that specialize in tomatoes and maybe other vegetables.
I recommend that people check out The Garden Watchdog before ordering from other companies.
http://davesgarden.com/products/gwd/
Remy