Types of ExternalitiesNegative externalities – costs to third parties other than buyers or sellers not reflected in the market priceDamage by industrial pollution to people and propertyPositive externalities – benefits to third parties other than buyers or sellers not reflected in pricesFire prevention, such as smoke alarms and fireproofingPecuniary externalities – effects of increases or decreases in the price of a good on existing customers as a result of changes in the demand or supply of a good