Thank you for your question.
Let's take the second part first:
"...If not, why are we (or were we) running out of phone numbers, even
though phone numbers have a billion combinations?"
The reason we are running out of phone numbers is because most people
have more than one number! Consider cell phones, pagers, fax machines,
second lines, teenager lines, internet connections and the like. And
many, many businesses have multiple incoming numbers for sales,
accounting, tech support, fax numbers or even fax on demand, toll
free, etc. Looked at in this manner, it becomes easy to see why 245
million people can begin to use up the pool of available phone numbers
- which are a little under 10 billion, by the way, since phone numbers
are 10 digit. Area codes do not start with 0 and some number
combinations are not used, of course, so the actual number is a bit
less. But more than the billion you had mentioned.
The Canadian National Post says:
"...Toronto began dialing 10 digits for local calls this month and
this spring will also get a new area code, 647, to keep up with the
demand for new numbers.
Vancouver and Montreal are also getting new area codes, with other
Canadian cities to follow. And many other major urban centres in North
America are now using 10-digit dialing for local calls. But when
cities need a third area code, there may not be one available. ''The
10-digit number is a limited resource which is running out fast,''
said Eric B. Morson, an expert on the phone numbering system.
''People don't recognize the looming crisis that is right down the
road,'' Mr. Morson said.
Park Davis, president of Ottawa's Canadian Numbering Administration
Consortium Inc. -- which allocates phone numbers -- said there are 18
to 20 possible phone numbers for every man, woman and child in North
America. Still, he said numbers are fast running out.
''It's conceivable that we may run out of area codes and numbers
within six years,'' Mr. Davis said. ''There is a great deal of debate
as to how long this resource will last. Some people say as early as
six years, some say as late as 20 years.''
The phone number shortage comes as users of cellular phones, pagers,
fax machine and Internet lines continue to suck up numbers at
breakneck pace. New companies competing to provide phone service also
tie up far more numbers than go into service.
In the past six years North America has assigned 143 new area codes.
The North American Numbering Plan Administration -- which assigns new
area codes -- warned in its 1999 Exhaust Study that with accelerated
growth, North America's last three-digit area code will be in use by
2006. With moderate growth, the area code bank will be empty in 2007.
Under pressure from phone companies, the group later toned down its
prediction, saying the continent has area codes to last through
So, you will also note that area codes are not only for the US, but
are shared with our neighbors.
And Wired news:
"...Originally a hacker's tool to make free long distance calls, VoIP
is set to emerge as the next big thing in commercial telecom. Heather
Tinsley of Telegeography estimates that as much as 10 percent of all
international voice traffic was carried over IP in 2002.
The phone companies insist that VoIP has the potential to eat up
10-digit numbers faster than cell phones, fax machines and pagers did.
This would hasten the day North America runs out of unique phone
numbers, requiring an entirely new numbering scheme..."
Now, Social Security numbers:
How Stuff Works:
Do the digits in my social security number represent anything in particular?
"Social security numbers (SSNs) are not random numbers. They are
assigned regionally and in batches.
The nine-digit SSN, which has been issued in more than 400 million
different sequences, is divided into three parts:
Area numbers - The first three numbers originally represented the
state in which a person first applied for a social security card.
Numbers started in the northeast and moved westward. This meant that
people on the east coast had the lowest numbers and those on the west
coast had the highest. Since 1972, the Social Security Administration
(SSA) has assigned numbers and issued cards based on the ZIP code in
the mailing address provided on the original application form. Since
the applicant's mailing address doesn't have to be the same as his
residence, his area number doesn't necessarily represent the state in
which he resides. For many of us who received our SSNs as infants, the
area number indicates the state we were born in. You can find out
which area numbers go with each state here.
Group numbers - These two middle digits, which range from 01 through
99, are simply used to break all the SSNs with the same area number
into smaller blocks to make administration easier. (The SSA says that,
for administrative reasons, group numbers issued first consist of the
odd numbers from 01 through 09, and then even numbers from 10 through
98, within each area number assigned to a state. After all the numbers
in group 98 of a specific area have been issued, the even groups 02
through 08 are used, followed by odd groups 11 through 99.)
Serial numbers - Within each group designation, serial numbers -- the
last four digits in an SSN -- run consecutively from 0001 through
According to the SSA, the numbers are not recycled. Upon an
individual's death, the number is removed from the active files and is
not reused. Recycling numbers might become an issue someday, but not
any time soon -- statisticians say that the nine-digit SSN allows for
approximately one billion possible combinations!..."
So, since the numbers are not recycled, digits will have to be added
sometime in the future to accommodate for new births. However, there
appears to be a pool of numbers still available for assignment:
Structure of Social Security Numbers
last modified May 15, 2001
"...The following table is now out of date. The SSA currently
maintains an up-to-date version. I'm leaving the old one here in case
the SSA's version goes away. As of 2001/5/15, the SSA lists group
numbers as high as 768 as having been issued.
001-003 NH 400-407 KY 530 NV
004-007 ME 408-415 TN 531-539 WA
008-009 VT 416-424 AL 540-544 OR
010-034 MA 425-428 MS 545-573 CA
035-039 RI 429-432 AR 574 AK
040-049 CT 433-439 LA 575-576 HI
050-134 NY 440-448 OK 577-579 DC
135-158 NJ 449-467 TX 580 VI Virgin Islands
159-211 PA 468-477 MN 581-584 PR Puerto Rico
212-220 MD 478-485 IA 585 NM
221-222 DE 486-500 MO 586 PI Pacific Islands*
223-231 VA 501-502 ND 587-588 MS
232-236 WV 503-504 SD 589-595 FL
237-246 NC 505-508 NE 596-599 PR Puerto Rico
247-251 SC 509-515 KS 600-601 AZ
252-260 GA 516-517 MT 602-626 CA
261-267 FL 518-519 ID 627-645 TX
268-302 OH 520 WY 646-647 UT
303-317 IN 521-524 CO 648-649 NM
318-361 IL 525 NM *Guam, American Samoa,
362-386 MI 526-527 AZ Philippine Islands,
387-399 WI 528-529 UT Northern Mariana Islands
650-699 unassigned, for future use
700-728 Railroad workers through 1963, then discontinued
729-799 unassigned, for future use
800-999 not valid SSNs. Some sources have claimed that numbers
above 900 were used when some state programs were converted to federal
control, but current SSA documents claim no numbers above 799 have
ever been used.
As of Feb 10, 1999 the most recent area numbers to have been assigned
include 650-658, 667-675, and 680. This list is from the SSA's web
site, which shows the highest group number assigned for each area..."
So, it seems there is some discrepancy, but it appears that number at
least from 729-999 have not yet been used.
running out of phone numbers
running out of social security numbers
"social security number" +"running out"
number of digits +"social security number"
I trust my research has provided you with a bit of insight into
available phone and social security numbers. If a link above should
fail to work or anything require further explanation or research,
please do post a Request for Clarification prior to rating the answer
and closing the question and I will be pleased to assist further.