I'm looking for estimated current household penetration rates of
mobile phones, PC's, and PDA's in Europe, North America, and Asia. 
(I'm defining penetration as the installed base of each of these
devices divided by total households.)

Penetrations of consumer electronics technologies are interesting to
track.  In the U.S., initially the home market will seem saturated,
then they acquire multiples of each product as the technology becomes
less expensive.  By 2000, there were more than 5.6 radios per home and
2.2 television sets per home.

Here's what we know about each technology:

Personal computers
-------------------
U.S.: 61% 
Western Europe: 57% (Sweden highest at 74%; Spain lowest at 37%)
Asia: highly varied
China: 2.5%
Japan: 40-44%
South Korea: 68%
Hong Kong: 59%
Australia: 65%

Sources:

Europe PC (August, 2002):
http://www.europemedia.net/shownews.asp?ArticleID=12164

U.S. PC penetration (March, 2002)
http://sanjose.bizjournals.com/sanjose/stories/2002/03/18/daily2.html

China:
http://www.idc.com.sg/Press/2001/AP-PR-PRC-subregionQ2.htm

Rest of Asia:
www.acnielsen.co.th/news.asp?newsID=49

Japan (Nov. 2000)
http://ne.nikkeibp.co.jp/english/2000/11/1109pc_dsp.html

Cellphones
-----------
North America:  117% 
Western Europe: 114% 
Asia Pacific (with China): 46% 

For cellphone penetration we've used one data source, the EMC World
Cellular Database (June, 2001).  To figure household penetrations,
these numbers were used:

HOUSEHOLDS:
U.S. 119.5 million (2000 U.S. Census + Canada)
Western Europe: 322.2 million
Asia:
China: 519.6 million 
Japan: 118.5 million
All Asia-Pacific: 718.9 million

Cellphone data source:
http://www.cellular.co.za/analysts/07182001-emc_forecasts_subscribers_to_top.htm

PDAs
------

PDA penetration rates are more difficult to obtain publicly, though
there are studies from a variety of vendors available.  Computer
Industry Almanac has a report available that's updated twice each year
and costs $1,250:
http://www.c-i-a.com/wwpda.htm

Computer Industry Almanac estimates 2001 sales of 16.4 million units
worldwide; 6.6 million in the U.S.  Its press release notes one of the
problems in measuring PDA sales -- increasingly cellphones have
similar functions.  "PDA-Phones to Spur Worldwide PDA Proliferation"
(Jan. 4, 2002) is here:
http://www.c-i-a.com/pr0102.htm

Meta Group estimates that current penetrations in the U.S. are 10-15%
of knowledge workers in this IT Insights newsletter:
http://www.itworld.com/nl/it_insights/03262002/pf_index.html

Penetrations of that level would put PDAs per household in the 5-7%
range for the U.S., which is clearly the largest world market.

Google search strategy is similar for each of the technologies:
"personal computer" + penetration
"personal computer" + penetration + Japan

Best regards,

Omnivorous-GA

Great info on PC penetration, but less complete on cell phones and PDA's

China-related data are pretty old and inaccurate.

Here is update on mobile phones in China:

Nowadays, China Mobile possesses fixed assets of RMB 170 billion. By
the end of 2000, its entire capacity exceeded 76 million, and its
realistic number of the subscriber is over 65 million, the popularity
rate of mobile phone will reach 5.18%, call completing rate reaches
more than 99% and call failure rate is 1.3%. The annual operation
revenue was RMB 115 billion, the total amount of assets reached RMB
320 billion. The group company and its subsidiaries' network covered
nationalwide regions (cities) and over 96% of counties (cities). In
international roam, has opened automatic roam service with 95
telecommunication operators in 56 countries and regions. Up to April
2001, the number of China Mobile 's subscriber reached over 0.1
billion.

Check the whole artile at
http://www.acmr.com.cn/english/industry%20reports/brev1.htm