檢視外部性的原始碼

[[File:外部性.jpg|缩略图|[https://image.baidu.com/search/detail?ct=503316480&z=0&ipn=d&word=%E5%A4%96%E9%83%A8%E6%80%A7&step_word=&hs=0&pn=0&spn=0&di=171270&pi=0&rn=1&tn=baiduimagedetail&is=0%2C0&istype=0&ie=utf-8&oe=utf-8&in=&cl=2&lm=-1&st=undefined&cs=1715564104%2C1595867793&os=632739101%2C2603155901&simid=0%2C0&adpicid=0&lpn=0&ln=1643&fr=&fmq=1621040778360_R&fm=&ic=undefined&s=undefined&hd=undefined&latest=undefined&copyright=undefined&se=&sme=&tab=0&width=undefined&height=undefined&face=undefined&ist=&jit=&cg=&bdtype=0&oriquery=&objurl=https%3A%2F%2Fgimg2.baidu.com%2Fimage_search%2Fsrc%3Dhttp%3A%2F%2Fimage.xmcdn.com%2Fgroup52%2FM0A%2F3D%2F1A%2FwKgLcFv-JDaAaAGwAAFNhbhGF8c880.png%3Fop_type%3D4%26device_type%3Dios%26upload_type%3Dattachment%26name%3Dmobile_large%26refer%3Dhttp%3A%2F%2Fimage.xmcdn.com%26app%3D2002%26size%3Df9999%2C10000%26q%3Da80%26n%3D0%26g%3D0n%26fmt%3Djpeg%3Fsec%3D1623632799%26t%3Dd94b4c9d68b83fd81cffed8577f81b82&fromurl=ippr_z2C%24qAzdH3FAzdH3Fooo_z%26e3Bowg2s75st7xtg2_z%26e3Bv54AzdH3Fxt_899m99dd8c09cc9mlba_z%26e3Bip4s&gsm=1&rpstart=0&rpnum=0&islist=&querylist=&force=undefined 原图链接][https://www.wangluoliuxing.com/xi_1446442215745546980.html 来自网络流行榜]]]
'''外部性'''又称为溢出效应、外部影响、外差效应或外部效应、外部经济，指一个人或一群人的行动和决策使另一个人或一群人受损或受益的情况。经济外部性是经济主体（包括厂商或个人）的经济活动对他人和社会造成的非市场化的影响。即社会成员（包括组织和个人）从事经济活动时其成本与后果不完全由该行为人承担。分为[[正外部性]] (positive externality) 和[[负外部性]] (negative externality)。正外部性是某个经济行为个体的活动使他人或社会受益，而受益者无须花费代价，负外部性是某个经济行为个体的活动使他人或社会受损，而造成负外部性的人却没有为此承担成本。