This supports the theory that iPhone is particularly effective at undermining traditional text-messaging.

FORBES: Text-messaging Volume of iPhone Owners Declining Sharply in Finland

Situational leadership theory holds that leaders are most effective if they adopt different leadership styles depending on the task and the people they are leading.

FORBES: Can 'Feminine' Women Make It To The Top?

The theory sounds great: Insurers that provide the most cost-effective care can lower premiums and attract more buyers.

FORBES: Medicare Vouchers Won't Reduce Health Spending

In theory, selling personal insurance and savings products through bank branches is more cost-effective than using networks of agents and brokers.

ECONOMIST: In the land of milk and money | The